Sift first three dry ingredients; cream butter, sugar, eggs and extract. Add chocolate. Add dry ingredients alternately with milk. Divide dough in half. Cover tightly and chill for 2 hours. Shape in 1 inch balls and roll in powdered sugar. Bake at 350 for 12-15
minutes on greased cookie sheet. These "crackle" during baking, so that the appearance is that of a "cracked" surface with powdered sugar on the higher parts of the surface.