Beat butter and sugar until light and fluffy. Knead in almond kernels, bitter almond flavoring and flour. Refrigerate dough for at least half an hour.
Preheat electric stove to 175 °C. Roll out dough to about 1/2 cm thick and cut into pieces about 5 cm long and 1 cm wide.
Mix the egg with a fork. Brush the sticks with it and roll them in the sugar. Place them a little bit apart on a baking tray covered with parchment paper and bake in the oven at 175 °C (gas: level 2) for about 10 minutes.
Shelf life: 4-5 weeks