How to give brownies a smooth, glossy top

the secret to getting a glossy papery skin on your brownies is to get the sugar very well dissolved and or dispersed through your batter if you can see or feel lots of really big sandy grains of sugar in your batter you're probably not gonna get that skin if you really dissolve your sugar and you're still not getting that nice glossy skin then i would guess that maybe you don't have enough sugar or maybe you have too much water or you don't have the right kind of sugar it has to be sucrose or perhaps some similar sugars but most of the common syrups in the kitchen will not do it honey brownies yum contrary to what a lot of very smart people believe brownie skin does not result from using a specific kind of fat and it does not result from whipping air into the batter it is chiefly about the sugar and secondarily the water we're going to prove it with experiments and the experiments will also explain why other people are wrong about this because in a way they're not wrong whipping the eggs and the sugar a lot can help you get brownie skin using lots of solid chocolate in your batter can help you get brownie skin as is so often the case in cooking people's methods work it's simply their reasoning or their explanation of the method that is false and they're not wrong because they're stupid they're wrong because they have important things to do in their lives they can't blow a whole week doing 50 test bakes to isolate the variables and figure out which one is causal only a lunatic like me does that so let's go to start we're going to need a baseline brownie recipe right mark bittman here has the basic no frills and somewhat old-fashioned version of nearly every dish in the western culinary canon here we'll bake this four ounces of unsweetened chocolate and a stick of butter melt in a pan or in the microwave in goes a cup of sugar and two eggs let's see what else a splash of vanilla and a pinch of salt and finally a half a cup of flour mix it smooth bake it and it looks like this no skin boo now let's try that same exact bitman recipe again but this time we'll swap out the granulated sugar for this powdered sugar or icing sugar as the brits would say simply an extremely fine grain of sugar and it's fluffier more aerated so you gotta use like one and three quarter cups to get the same weight as a single cup of normal sugar mix that up and note how much more viscous the batter is bake that and beautiful papery skin look at the difference but i have questions powdered sugar isn't just sugar there's also a small amount of corn starch in there it serves as an anti-caking agent could the cornstarch be helping the crust maybe absorbing water helping the skin dry well let's see if we can make our own powdered sugar without cornstarch in it i blitzed this for literally a half hour and it's nowhere near as fine as powdered sugar but it is finer so let's make the bitman recipe with it same quantity of sugar by weight and that's not the best skin i've ever gotten on brownies but that batch does have some skin now let's use the food processor sugar again but this time add seven grams of corn starch if you look at the nutritional label you can see that it has 29 grams of sugar but 30 grams of carbohydrates so we know that that remaining gram can only be cornstarch it's 1 30 corn starch anyway identical to the previous batch with no corn starch corn starch is not why powdered sugar gives us great skin i used to think it was but the real reason is any super fine grain of sugar is going to dissolve really easily into the batter and how do we know that's the real reason well let's talk to dr pia sorensen at harvard co-author of the new book science and cooking physics meets food from homemade to oat cuisine the sort of magic power of sugar is that you can dissolve a lot of sugar in water you can actually dissolve twice the amount by weight of sugar in any amount of water so doc suggests we try making the bitman recipe as written with normal granulated sugar and i'm just barely bringing this together i'm certainly not whipping in air the only thing we'll do differently this time is just let it sit for a long time in fact i just mixed it up and then i went to bed when you mix all the things together the sugar is going to dissolve in the water in the batter and even if you're not actually adding water right you're sort of indirectly adding water because there's water in the egg there's even some amount of water in the flour right there's like 15 water in the flour and that little bit of water in these ingredients is enough to dissolve the sugar now you might normally accelerate the dissolution process with a little bit of heat or maybe with agitation stirring it really aggressively but we want to isolate the variables here heat could cause other chemical changes in the batter and whipping it could get a lot of air into the batter so that's why we're just mixing it up and just letting it sit still for a long time the next morning you can see how much more viscous it is dissolved sugar makes liquids thicker bake it and it's a little lumpin but that is shiny brownie skin again here's that same recipe mixed up and immediately baked here it is mixed up allowed to sit overnight and then baked when the sugar is well dissolved you get skin it's almost that simple but why right why does dissolving the sugar get us the skin so what i think happens is that here is this batter right sitting in a pan it has a little viscosity then you heat it and any air that is trapped in the batter is going to try to escape but already at the very surface you have already kind of dehydrated that a little bit so it's already forming a little bit of a shell that is trapping the air that is coming up from inside the guts of the brownie and then there's this delicate balance where you want this very top layer to be dehydrated enough and viscous enough so that it both can lift a little bit but also not break and just sort of go poof right away indeed the latter scenario is exactly what we see happening in our batches that don't have skin they are pock marked with little popped bubbles here's a batch that for reasons we'll soon discuss has some areas with skin and some areas without skin look under the microscope these skinless areas are just full of little holes where the surface layer could not hold back the gas the gas pushed through and left a little hole if we look at the areas that do have skin we can see the surface here has dried in the oven to a hard shell gases pushed up under it stretching it taut and smooth like a balloon but the balloon never popped it stayed solid it stayed smooth and smooth things reflect light much more directly that's what gloss is and what goes better with a glossy brownie let's thank the sponsor of this video trade coffee in the space of a year trade has turned me from a coffee noob into a total nerd now when i fill out their online quiz i know exactly what kind of coffee i like and they send me more of it all kinds of fun things from the top roasters coffees i never find on my own having trade send me lots of different stuff helped me to discover my own tastes i like more acidic coffees like this big surprise plus trade ensures that i'd never run out of coffee because it comes right to my door at regular intervals their packaging is compostable by the way you can do us both a favor and save fifty percent on your first bag when you sign up with my link and code in the description if you don't love it they'll send you a different bag for free that fifty percent offer is good for the first hundred of you who use my link and my code rogucia50 shipping is also free thank you trade now let me show you a batch that i made with powdered sugar so that the sugar would dissolve really thoroughly and i increased the sugar quantity by about a third the surface area dried so hard and candy-like that the skin couldn't even balloon very much with the gas it just sat there a solid impenetrable wall in contrast here's a batch that i made with the bitman recipe with powdered sugar which normally gives you great skin but instead of increasing the sugar content i increased the water content just like a quarter cup of water there and look even though that sugar is very well dissolved no skin the batter was too loose and wet the surface didn't dry in time to hold the gases back we get a field of popped bubbles instead so if you've got a brownie recipe that you really like but it doesn't give you that nice skin the first thing that i would try is just swapping out the sugar for powdered sugar if that doesn't work try increasing the sugar a little bit and or decreasing the water a little bit and if your recipe doesn't call directly for water try removing one of the egg whites you need the emulsifiers in the yolk but the protein in the white is less important and it's mostly water so you can just cut it out you could also get rid of the water that's in the butter butter is 15 or 20 percent water and you can get it out by switching it with clarified butter which has no water in it or you could brown the butter brown butter tastes great in brownies and in the course of browning it you're gonna evaporate most of its water or you could swap the butter for oil no water and oil right this batch i made with powdered sugar and oil instead of butter inferior flavor but even better skin this experiment also suggests that the type of fat is irrelevant to skin it's merely a matter of the water that the butter brings with it so why do so many people say that cocoa butter is the key to brownie skin melting lots of solid chocolate into your batter that gives you the skin lots of people claim that i suppose one reason could be that cocoa butter is a form of fat that brings little if any water with it so if you swap out the butter in your recipe for cocoa butter you can have less water in the batter and as a result that surface of the batter will be able to dry faster in the oven it could also be that that extra step of heating and melting the chocolate helps to dissolve your sugar heat accelerates dissolution and if you put the sugar in the pan with your chocolate and your butter and such as you're melting all of it that's going to help dissolve the sugar plus if you're melting sweetened chocolate like chocolate chips then it could be the sugar that's already in the chocolate helping you out and that sugar is already dissolved so you don't have to you're not you're not running into this problem with the sugar not dissolving and that is then um again causing that crust likewise this is probably why people think whipping air into the batter will give you skin it does but not because you've aerated the batter it's because this extra step of beating the sugar and the eggs until foamy also agitates the sugar in the presence of water helping it to dissolve more smoothly though the crust you get from that technique is not as shiny i would guess that's because the very small bubbles that you beat into the batter make the surface less smooth but it's still good and dry so it's crusty because the sugar was well dissolved into a minimal amount of water all of this raises the question why not just make brownies with a form of sugar that's already dissolved aka a syrup well here's the bittman recipe again with no sugar but an equivalent amount of corn syrup by weight no skin at all on those here's the same experiment but with honey instead of sugar no skin at all why not well maybe we have too much water in the batter honey and corn syrup are both like 20 water and we know from our other experiments that having too much water in the batter means that the surface layer won't be able to dry in time to form a crust so let's try boiling the water out of the honey mix up the batter bake it and yikes well maybe something different is happening on the molecular level here honey and corn syrup are mostly glucose and fructose and other sugars that are not sucrose cane sugar is sucrose so let's try making a pure sucrose syrup you need a little bit of water to get it dissolving but then i boiled it to about 240 fahrenheit which according to candy making references should mean that most of the water is gone mix up the batter bake the brownies and no skin dry batter fully dissolved sucrose no skin why not sucrose it's essentially two rings linked together it's one glucose ring and one fructose ring and they're held together by one single bond and that's it and that bond is easily broken with acid or with heat a little heat in a not particularly acidic solution won't do much at least if you don't leave it in there for very long but the kind of heat necessary to create a low moisture sugar syrup what that does when you then heat it is it pretty quickly breaks that bond and then you get what's called invert sugar which is really just a solution of fructose and glucose that's it and as we've previously established those sugars don't make brownie skin one more experiment here's the bittman recipe with powdered sugar which would normally give us a great skin but i'm going to drop in just a little glug of honey just a little spoonful and that is this batch the brownies with some skin and some not skin even a small amount of sugar that isn't sucrose disrupts that skin formation why well this is just an educated guess now but dr sorensen suspects that what's happening is when the sucrose dries on the surface of the brownie it recrystallizes a little bit and that's at least part of why the resulting skin is so smooth and shiny and crispy you can imagine that there are all these molecules kind of floating around a solution and in order for a crystal to form it's a little bit like um almost like building a brick wall where all of the bricks sort of fit together perfectly now imagine if instead of a solution with molecules where they're all the same size imagine instead you have some of those but then you also have maybe even just a few of some other molecules that are not quite like a half brick but they're sort of just a slightly different maybe they're a little round and now you want to build that brick wall and have it kind of stick together you can imagine that it's not going to fit perfectly there's going to be little little crevices and a little air here and there and it's not going to stick together as nicely so you're not going to be forming those little crystals again because those smaller different ones are interrupting the crystal structure so i think that is what the honey does that's what corn syrup does i buy it there's only one hitch though in my previous recipe video linked in the description i showed you the original brownie recipe that i came up with in the course of doing all these experiments it's got great skin and i used powdered sugar in it but i also used sweetened condensed milk why doesn't that disrupt the crystal structure well condensed or evaporated milk is conventionally made in a vacuum pan you boil it in a low atmospheric pressure environment and that lowers the boiling point so you can drive off the moisture at a much lower temperature that isn't going to really affect the flavor of the milk so much the fact that my recipe got me skinned suggests that the manufacturer of this specific brand at least uses real cane sugar or some other kind of sucrose and that they dissolve it into the milk either in the vacuum pan or later at some relatively low temperature in either case a temperature low enough to not break the intramolecular bond of the sucrose and of course the sugar in milk is lactose which is also a two-ringed it's not a one ring they're different to ring structures than sucrose but still it may be less disruptive right than than having all these wandering structures in there however it occurs to me that some cheaper manufacturers of sweetened condensed milk might boil their product at a higher temperature to save time or they might use corn syrup instead of the more expensive cane sugar in either case that would disrupt your skin so if you're using my recipe and not getting skin maybe try a different brand of sweetened condensed milk lastly there's the issue of the molasses in my recipe i wanted that nice flavor you get from brown sugar but i wanted the crust you get from powdered sugar so i used powdered sugar and i called for just like a couple of teaspoons of molasses because after all brown sugar is just sugar with molasses in it molasses itself is a byproduct of sugar making and as a result it has a lot of sucrose in it but depending on what brand you buy and how it was processed it might have lots of other sugars in it as well so if you're doing my recipe and not getting good skin this may be a reason why and or maybe you're using too much here's two batches of my recipe this one has about half as much molasses as this one and this one is shinier maybe that's the reason why and of course if you just want brownies with great skin but you don't have to worry about any of these variables just buy boxed brownie mix the mixes usually give you great skin because their water to sugar ratio is carefully formulated and because the sugar is very fine look how powdery that mix is tiny sugar crystals that'll dissolve even better than coffee into water don't forget to save 50 on your first bag from trade with my link and code in the description and happy skin hunting because that doesn't sound terrifying

Channel: Adam Ragusea

Views: 1,158,243

Keywords: brownie crust, crusty brownies, shiny brownies, glossy brownies, brownie skin

Id: qpF5B_jHZrw

Length: 17min 50sec (1070 seconds)

Published: Mon Feb 01 2021