1/3 cup butter
2/3 cup granulated sugar
1 teaspoon vanilla extract
1/3 cup unsweetened cocoa powder
1 3/4 cups all-purpose flour
1/2 cup mini semisweet chocolate chips
1/4 cup chopped walnuts
1 egg yolk, beaten
1 tablespoon water
2 teaspoons baking powder
Beat butter until soft, then add sugar and baking powder. Beat in eggs and vanilla extract. Add cocoa and as much flour as you can by mixer. Add the remainder by hand. Stir in chocolate chips and nuts.
Divide dough into two equal parts. Shape into 9 x 2 x 1 inch loaves. Place on sheet 4 inches apart. Brush with mixture of water and yolk.
Bake at 375 degrees F for 25 minutes. Cool on sheet for 30 minutes.
Cut loaves into thick slices diagonally. Lay cut side down and bake at 325 degrees F for 15 minutes. Turn over and bake other side for 10 to 15 minutes until dry. Cool. Store in an airtight container.