Vanilla Dough:
2 cups flour
1/2 tsp baking powder
1/4 tsp salt
8 tbsp butter, softened
1 cup sugar
1 egg
1 1/2 tsp vanilla
Chocolate dough:
1 cup flour
1/2 cup unsweetened cocoa powder
1/2 tsp baking soda
1/4 tsp baking powder
1/8 tsp salt
8 tbsp butter, softened
1/2 cup brown sugar (packed)
1/2 cup granulated sugar
1 egg
1 tsp vanilla
Directions:
Vanilla -
Mix the flour, baking powder, and salt together with a whisk. Set aside. In a large mixing bowl, beat the butter and sugar with an electric mixer until light and fluffy, 3 to 4 minutes. Beat in the egg and vanilla. On low speed, beat in the flour mixture until just incorporated. Form the dough into a log about 2 inches in diameter. Set aside.
Chocolate -
Mix the flour, cocoa, baking soda, baking powder, and salt together thoroughly with a whisk. Set aside. In a large mixing bowl, beat the butter, brown sugar, and granulated sugar with an electric mixer until smooth and creamy, but not fluffy (less than 1 1/2 minutes). Beat in the egg and vanilla. On low speed, beat in the flour mixture and mix just until incorporated. Form dough into a log the same length as the vanilla log. If the dough is too soft and sticky to handle, place it in the freezer to firm.
Shaping the skulls -
Reshape each log of dough so that it is skull shaped rather than round: make one side narrow for the chin and jaw, and leave the other side wide for the cranium. Wrap and refrigerate the chocolate dough. Form features in the vanilla dough, using the handle of a wooden spoon to poke holes for eyes through the entire length of the log. Form the nose with a skewer, poking two holes for nostrils. Form the mouth by inserting a narrow table knife and wiggling it back and forth to lengthen and widen the opening. Don't try for perfection: irregular holes make the best and weirdest skulls. Wrap and refrigerate the vanilla dough. Chill both doughs at least 2 hours, preferable overnight.
Position rack in upper and lower third of the oven. Preheat the oven to 350 degrees. Cut the chocolate dough into 1/8-inch slices and place them at least 1 1/2-inches apart on the baking sheets. Cut the vanilla dough into 1/8-inch slices and place 1 slice on top of each chocolate slice. Bake until pale golden at the edges, about 12 minutes. (Rotate the pan if necessary.)