These are fundamentally notes on top of the recipe for croissants that's in the book "Pâtisserie! 210 recettes • 3200 photos L'ultime référence" in French. And I need to make notes so I don't forget what I've learnt about croissants so far.
By "dry" butter, I mean butter that's at least 84% of fat. The butter you'll find in most places will be less fat and more watery. You can use the more watery butter as it comes. But it's (much?) better if you use dry butter, or if you dry some regular butter.
To dry some regular butter, knead it in your hands and shake off the water that's coming out of it. I find Canadian butter very very watery.
I don't use the milk powder. It's in the original recipe. I'm not buying milk powder just for making croissants and I can't really imagine why it would make them better. Also I really don't want to use baby formula powder!! Anyways, it works fine without it.
Don't put the sugar before the salt, or at the same time. Sugar melts easier than the salt into water. If you put the sugar first, you'll have a harder time melting the salt.
If you see traces of the yeast, or salt or sugar in case you didn't wait until they were fully melted in the water, knead longer. It can take from 4 minutes to 20 minutes at medium speed in a robot. Melting the salt and the sugar in the water really helps. If you knead the dough longer, it becomes tougher, therefore it'll require more resting time! So, melting the salt and the sugar in the water is not "just to bother you", it has actual purpose!
Shape the dough like a rectangle and wrap it so it doesn't dry. Put it in the fridge for at least 2 hours.
I generally let it rest there the whole night.
Here that resting step is very important. After you have kneaded the dough, it has likely become very strong, very tough, hard to pull, not very elastic. So you need to let it rest for quite a while since you'll have to roll it a lot. Also, you cannot let it rest at room temperature because the yeast would be way too active and it'd eat too much of the sugar. And you actually do not want bubbles in your dough yet. And since you can't add the yeast at a later stage, you're stuck with letting it rest in the cold.
Flatten the dough to a thickness of 7 mm (about 1/4 inch, if you dare use those insane archaic imperial units, sorry I don't mean to offend you, but in 2019 those units are extremely outdated, imprecise, and anti-scientific, even in 1999 they already were).
Try to keep the shape of a rectangle. You're going to imprison the butter in that rectangle!
Shape your "dry" butter into a rectangle that it's half the size of the dough. By half the size, I mean, don't make your life harder by picking the harder half. Also, make it actually slightly smaller than half.
The butter and the dough should have similar consistency: the butter should not be much harder than the dough. If it is, either cool down the dough or warm up the butter (just a little).
Fold the dough so you trap the butter inside. Seal the butter in the dough. Don't trap air with the butter, or at least try to avoid putting air, because if you do it'll mess with you.
If your butter it too hard or contains chuncks that are harder than others, it may pierce the dough. You do not want that to happen! If your butter is uneven or too hard, you can knead it (or whip it a little if you have a machine). You really want your butter to be even and not too hard.
If it's too hard, it means it's too cold. To speed up the process, you can cut it into pieces and squeeze the whole thing with your hands. That'll warm it up and you can squeeze it until it becomes very even. If you warm it up a little too much, you can still trap it in the dough, just let them cool down in the fridge before rolling/folding.
If your dough with the imprisoned butter is ready to be flatten, do it now, otherwise let it rest in the fridge.
When you flatten the pastry, the butter shouldn't move to one side or the other. The whole thing has to flatten evenly, hence the importane of the dough and the butter to have similar consistency.
Flatten the pastry to about 6 mm (that's slightly less than 1/4 inch, while 7 mm was slightly more than 1/4 inch).
Fold it so that you end up with 4 layers. Look at videos or pictures on the internet if you don't already know how! Or you'll mess it up.
If your butter moves too much inside, try to just even it, and let it cool down a bit in the fridge.
I've found a quite awesome video on Youtube to show you the things for which words just can't compete with video.
In there they (seem to) use a ratio butter/flour of 62.5%, while Christophe Felder's recipe is at 70%. This means Felder's is fatter, and probably better although harder to make!
They use fresh yeast, which I don't like to use because
Put the pastry in the fridge for 1 hour (or more). Make sure it doesn't dry up!
It's now pastry, not just dough.
Flatten the pastry to 6 mm. Fold it so that you multiply the number of layers by 3 or 4. (I do 4 if I see that it's easy enough, otherwise 3).
At the end, you end up with 12 layers of butter, or 16.
Let the pastry rest in the fridge for 1 hour again (or more). Again, don't let it dry!
Flatten the pastry to 4 mm. That's 5/32 inch. (Seriously, I hope you see how messed up imperial units are...)
Well, before, the 6 mm were not that important: if you did 8 or 9 mm, it wouldn't matter that much.
Here, you really want something pretty thin. Don't try to do something like 2 mm. That would be too thin. Your pastry would likely dry up too fast. The butter might go out as the layers may tear too easily.
You really don't want something too thick. There's a trick though. If you think you can't flatten it to 4 mm for whatever reason, do the folding 3 times instead of 2, so you can go to 12 mm instead of 4. But you might end up with pretty big croissants.
Cut isosceles triangles. (Don't cut equilateral triangle.) You want two long sides, one short side. Roll the short side towards its opposite vertex. Put the vertex under the croissant so that it's stuck (and doesn't unroll later).
There you have your croissants!
In the video mentioned above, they cut a little into the triangles at the top vertex and at the base (and they add a chocolate bar). You can do those if you want but it's very optional. It mostly means more work. Cutting into the top vertex makes that point a little crispier, which is normally a good thing (but is it worth it?). I'd say it's probably worth it for very large croissants, and quite irrelevant for tiny or small ones. Cutting into the base makes the base artificially wider, in my experience it's not very useful except if you really want your croissants to be a little longer and rise a little less.
Let them rise at room temperature for 2 hours.
After that, brush egg wash on (top of) them. (In the book, it's one egg plus one yolk. I don't bother with adding the yolk, I use only one egg. However adding the yolk would totally help and I totally get it: egg white is kind of hard to brush on the croissants, so adding egg yolk makes it easier. And also that would slightly change the flavours.)
Bake them at 180°C (360°F) for 12 to 15 minutes. More if you see they're not dark enough.
When they're baked (or almost baked), you can brush some pure caramel syrup on them, put them back in the oven and bake them 1 or 2 minutes (or until they're perfectly colored).
To make pure caramel syrup: make caramel with either only sugar, or sugar and water, and once you have your pure caramel, add water to give it the consistency of honey. When the pure caramel syrup is cooled down, if it's too thick, add some water (and either heat it up so it blends faster, or just wait... beware, it might take up to several days or even weeks in the worst case)
Do not try to make croissants less fat! The whole point of croissants is that they're fat! If you make them less fat, they won't be worth being eaten.
The salt is important to slow down the yeast, and when the yeast is slowed down, it does a better job at developing awesome flavours!
The croissants don't rise (or very very little) before the last step before baking. You don't want the dough to rise before the pastry is flatten into the shape of croissants (or the shape of whatever you want to use it for). That's one of the reasons why it's important to have a fridge.
In the summer, if it's hot in your kitchen and you don't have A/C, perhaps don't make croissants... It's really messy and difficult if the butter melts or becomes too soft in the pastry! If you really really want to make croissants while it's really hot, perhaps try cooling down your board with ice cubes in a bag before you put your pastry on it. And put the pastry in the fridge everytime you don't need it so that it remains cool.
Don't let the croissants over-rise. Or else when you brush egg on the croissants, they'll de-puff. If ever you see that they're de-puffing when you brush them, brush more gently, or perhaps just don't brush them. If you don't brush your croissants, they might look quite pale, and miss a bit of flavour. The egg wash adds some nice flavours to the croissants.