Mac Attack #18: Dark Chocolate-Espresso Macarons

I'm still obsessed with baking macarons.
And yes, I know, I still have not posted my basic recipe, but it just takes a lot of time, a lot of pictures, and so on. I will definitely try to post my version of the French Meringue method within the next two weeks....
Yesterday, the Mac Atttack challenge #18 ended (I would have posted it back then if I hadn't though that I have to post it on the 27th...).
It's my second challenge on Mac Attack, and it was quite a common theme: Chocolate. It was so common, I really didn't want to come up with something new, creative and crazy, so I took one of the two chocolate macarons recipes that I make a lot: Dark chocolate and Espresso macarons!

I started to love dark chocolate only about two years ago, same with coffee. But now I love both, especially, of course, when they are paired together! But again, I have to admit, I don't make macarons because I want to eat them, I make them because of the process of making them, because I want to give them away, hoping someone likes them, too! But of course, I eat them, too.
I always make only a small (one egg white) batch of macarons, otherwise it would really be too much.

Does anyone else know the problem that chocolate macarons shells (with cocoa powder in them) tend to be more flat?

For the filling, I used the ganache that I used for these macarons since I first made them. Nothing very special... The amount of cream and chocolate always varies a bit. I have it written down, but I always forget how I wanted to change it a little for the next time. I will write down the one I will do next time.

The macarons are very yummy and have a rich, bitter flavour... the filling is not sweet!
For an extra strong coffee flavour in the chocolate filling, I use extra strong espresso coffee and additionaly dissolved some instant coffee in it.
If you don't want a strong coffee flavour, you can use normal coffee.

For the shells, some confectioner's sugar is replaced and ground with a bit of cocoa powder and instant coffee. They are baked a little shorter on a little higher temperature. Recipe follows.

Dark chocolate-Espresso Ganache (fills about 12 macarons)
40 g	dark chocolate 72 %
40 ml	heavy cream (35 % fat)
2 tbsp	strong espresso
1 tsp	butter

Instructions:

1. Break chocolate into pieces and place it with the cream in a very small saucepan.
2. Let them melt together while stirring on very low heat.
3. Stir in the espresso and maybe some instant coffee.
4. Take away from heat and pour into a small glass. Let melt in a bit of butter and let it cool. When it is cool, put it in the fridge just until it has a good consistency for filling the macarons!

When the consistency is right (shouldn't be too hard, it should be smooth but not too liquid! Otherwise it will run down your shells) I place some ganache with a teaspoon (I don't use piping bags for that) on a shell, and place another shell on it. Put in the fridge for a day and take out 30 minutes before serving!
Time makes them get better.

Link to the challenge: here.