Combine almonds, almond extract, flour, and sugar until thoroughly mixed. Work in butter and egg yolk with hands; until well blended. Chill the dough for one hour.
Preheat the oven to 350 degrees F (175 degrees C).
Pinch off pieces of dough about the size of your thumb and shape into crescents. Place on greased cookie sheets and bake for about 16 minutes.
