After several more trials of making French Macarons I have learned a lot about the technique and finally produced a few that really look like the real ones. The technique is all about assuring that the air bubbles inside the batter are fine. Once heated up to 180 degrees this air will expand. Since we want to establish the little foot at the bottom this air needs to make its way out of the cookie exactly there at the bottom. This can only be achieved if the bottom is less dry than the rest of the cookie. That's why you have to let the cookies dry before baking them at 180 degrees. I found out that it's best to dry them in the oven at around 80 degrees for 30-40 min. But if you use simple baking paper as I did in the beginning the bottom will dry as well and then you won't get the foot but only cracks all over the cookie. So the trick is to use a silicon baking mat. This works as a heat insulator thus the bottom will not dry as fast as the top. In addition the batter must be relatively runny. If it's too much like meringue then it will have too much air inside and lead to cracks too.
So here is my recipe:
2 egg whites
2 tablespoons of icing sugar
50 g crystal sugar
50 g very finely ground almonds
(liquid food colour if you want to make coloured macarons)
Beat the egg whites at the highest setting of your electric mixer with the icing sugar until they hold their shape. Add the crystal sugar (and the food colour) using the lowest setting of the mixer. Afterwards add the almonds and mix them under also using the lowest setting of the mixer (the batter may become a bit runny but that's OK). Pour the mixture into a pastry bag with a large tip (standing the bag in a tall glass will help).
Line the baking tray with the silicon mat and use some butter to prevent the cookies from sticking on it. Pipe the batter in circles of 3 cm diameter making sure to leave enough space around each of them as they might run out.
Dry them in a non preheated oven at 80 degrees for 30-40 min. The surface needs to be dry when you touch it. Then heat the oven to 180 degrees. This will make the air inside the cookies expand. Bake for about 10-20 min until they are light brown.
You might need to experiment with the length of the drying and baking time depending on your oven.
I have used chocolate breakfast spread for the filling but jam will work too. Or you can make a filling using butter and cream.
Here are a few links for macarons recipes: