Place the butter, sugar, a pinch of salt, and vanilla sugar in a bowl. Mix everything well.
Add the egg yolks and stir them into the butter mixture. Gradually stir in the flour mixed with baking powder and knead to form a smooth dough. Let the dough rest in the refrigerator for 15–20 minutes.
Beat the egg whites with a pinch of citric acid until stiff peaks form, gradually adding the sugar and vanilla sugar.
Shape the dough into small cakes or circles, place half a walnut on each, and sprinkle with the remaining meringue. Bake in a preheated oven at 160°C (325°F) for about 20 minutes, or until lightly pink.
Once cooled, dip the cookies in melted chocolate or drizzle with it.
