These cakey cookies originate from North-Eastern France and have a typical lemon aroma.
The recipe is fairly simple. A variation is the addition of some ground nuts like almonds or hazel nut.
Some don't even add the lemon zest leaving the recipe as a bare génoise sponge cake.
You'll only need a special pan with shell-like depressions, usually 12 of them on the pan. The one I used has a shell size of 7,5 x 5 cm. The size (as with other recipes) can affect how well the batter cooks. This is something you have to eye-ball if the size differs.