Learn the science behind:
Some recipes are super flexible. Add a little more butter or flour to these chocolate cookies, and they’ll still look and taste great. And a little more or less butter to your brownie and it will slightly change in texture, but still taste great.
Others, are more finicky and somehow can only be perfection or disaster, with no, just fine, in between. Macarons definitely belong to that second category. In every cookbook and in so many places online they’re discussed as being one of the more finicky cookies out there.
But what on earth makes them so finicky (aside from our perfectionist expectations that is)?
What are macarons?
Macarons are very delicate, exquisite cookies consisting of two layers of baked almond meringue with a creamy filling inside. The filling is pretty flexible, you can use chocolate ganache, fruit purees, various types of buttercreams and firm meringues.
The challenge for making these cookies perfectly, are the shells. The shells are very delicate. The outside is just crispy whereas the inside is slightly soft. A perfect cookie is pretty flat on top, allowing it to lie horizontally. That top is also smooth, curved like a dome on the sides. At the bottom of these sides the macaron have what they call ‘feet’, a bubbly layer of meringue.
It isn’t easy to get this ‘perfect’ shape. But you can get a perfectly fine tasting one, that just doesn’t look as perfect. As such, it’s a great challenge for those up for creating the perfect cookie. In all honesty, we’re not those people, we like a good looking, delicious, but not perfect macaron. But if you are, we have some great resources for you at the end. And for all of us, we have an explanation for how these cookies work, so that you have some good science to share, while eating your perfect/less than perfect macarons!
How to make macarons
At the end of this post you’ll find an extensive recipe, for now, we’ll focus on how to create those shells. The shells are actually a type of egg white meringue. You make them by whipping up egg whites with some sugar and then folding through a mixture of almond flour and icing sugar. To stabilize and crisp up these meringues, you bake them in the oven.
Whipping up egg whites
Whipping up egg whites for meringues isn’t as much work anymore as it was before the invention of electricity. An electric mixer makes this very doable energy wise, however, it is a task you can’t walk away from.
When you’re whipping up egg whites you’re slowly unravelling the proteins inside an egg whites. These proteins then sit around all those beautiful air bubbles you’re whisking in. There they stabilize the air bubbles. It’s why you can whisk up an egg white, but not a bowl of just plain water (foam science).
If you unravel (denature) these proteins too much though they become a bit stiff as a whole. As such, you don’t want to over whip your egg whites. Anytime you want to mix something through the egg whites you want the foam to still be a bit flexible and soft. If the foam is too stiff it won’t give way to your almond flour and icing sugar mixture and be very hard to mix through.
Mix egg white foam with icing sugar and almond flour
The next crucial step is mixing that almond flour and icing sugar through. You’re using almond flour for taste. However, almond flour contains a considerably amount of fat, which isn’t good for an egg white foam. The almond flour won’t actually dissolve into the foam. Instead, it will just sit in between all those air bubbles. It is why recipes ask you to use a very fine variety, or even grind it down further. The particles need to be small enough to sit in between all those air bubbles without creating clumps in the final batter. These clumps and pieces would show up as uneven bits in the shell.
You mix the almond flour with icing sugar and there’s a good reason for icing sugar. Icing sugar is nothing more than just very finely ground granulated sugar. You want these small particles because it helps the icing sugar to dissolve within your egg white meringue, again contributing to a smooth foam. If you use granulated sugar it likely won’t dissolve quick enough and you’ll be left with sugar crystals in the final meringue!
Piping the batter
In order to create evenly sized domes, you have to pip the batter onto a tray. you might think that piping would actually push out all of the air out of the batter. And whereas some will certainly be pushed out, this batter is through enough to hold. It’s similar to using a Swiss meringue for instance.
This meringue batter is actually quite special. It will be fluid enough to create a flat top. However, it won’t run down into a puddle. Really, all the previous steps are such to create this ideal flow behaviour (the batter even has a yield stress! this is (partially) what holds it into that dome shape). Since this flow behaviour has to be just right, just slightly different ratios of water to sugar or even the temperature can impact this. It is why, creating a ‘perfect’ meringue isn’t impossible, but requires some optimization for your situation.
While the meringues are in the oven, which is at quite a low temperature by the way, the outside of the meringue will start to dry out. This drying out gives it that crispiness. The outside dries out quite easily and form this smooth top.
However, while the meringue is in the oven, the center will start to heat up and as a result the air bubbles within the center expand. Often, the small air bubbles will coagulate and form one or a few larger holes. Simultaneously, water evaporates. This water cannot disappear through the smooth sealed top so it likely goes through the sides. It is one of our hypotheses for the formation of those feet at the bottom!
if this gas expansion or moisture evaporation happens too fast or too much, it might result in a broken/cracked top of the macaron.
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Tips for a perfect macaron
There are various people online who have extensive guidelines for making a perfect macaron, though often with a disclaimer that every kitchen/ingredient choice might result in a slightly different result. We’ve grouped the better (more scientific) ones here for you!
Not so Humble Pie – Macaron 101
Ms. Humble has tried a lot of different macaron recipes and has written a mega long post on her journey. It’s a fascinating read for those interested. She even introduced a ‘scatter plot’ which I think is super cool of course.
She’s really tried a lot of different things and has come to a way of working that works well for her. That’s the kind of post I like, not repeating myths and tips others have mentioned, but actually checking whether they work for you!
One of my favorite parts is where she tested the difference between parchment paper and silicone mats. It’s not something you would commonly change but there’s quite a difference!
A great complete article style report in which the science of macarons is described. Two different types of sugar (regular granulated vs confectioners icing sugar) are compared when used in making macarons. Interesting article, although the literature study does seem to repeat several of the myths described above.