Ingredients

1 cup all purpose flour
1/2 teaspoon baking powder
1/4 teaspoon baking soda
pinch salt
pinch fresh ground pepper
6 tablespoons unsalted butter, softened
1/4 cup firm packed light brown sugar
1/4 cup granulated sugar
1 large egg yolk
1 teaspoon vanilla extract
1 ounce unsweetened chocolate, melted in pan over
simmering water

Directions

Sift flour, baking powder, baking soda, salt and pepper together.
Cream together butter and sugars until light and fluffy. Add egg
yolk and beat until mixture is well blended. Bet in vanilla and
chocolate. Add dry ingredients and mix at low speed or by hand
until well blended.

Form dough into 1 1/2 inches diameter log; wrap in waxed paper and
chill for 3 hours to 2 days. Or store in freezer until needed.

Preheat oven 375F. Slice dough 1/8 thick with sharp knife. Place
1 1/2 inches apart on ungreased baking sheet and bake in center of
oven for 7 to 9 minutes. Tops will show no fingertip prints when
pressed gently. Cool on wire racks and store in air tight container.