1/2 cup butter, melted
1/2 cup white sugar
1/2 cup brown sugar
1 teaspoon vanilla extract
3 1/2 cups all-purpose flour
1/2 cup unsweetened cocoa powder
3 teaspoons baking powder
1 teaspoon baking soda
1/4 teaspoon salt
1/2 cup miniature semisweet chocolate chips
1 1/2 cups chopped nuts (walnuts, pecans, hazelnuts, etc.)
Preheat oven to 350 degrees F (190 degrees C). Grease baking sheets, or line with parchment paper.
In a large bowl, cream together the butter and sugars until smooth. Beat in the eggs one at a time, then stir in the vanilla. Combine the flour, cocoa, baking powder and baking sda; stir into the creamed mixture until well blended. Dough will be stiff, so mix in the last bit by hand. Mix in the chocolate chips and nuts.
Divide dough into two equal parts. Shape into loaves. Place onto baking sheet.
Bake for 25 to 35 minutes in the preheated oven, or until firm. Cool on baking sheet for 30 minutes.
Using a serrated knife, slice the loaves diagonally into 1 inch slices. Return the slices to the baking sheet, placing them on their sides. Bake for 10 to 15 minutes on each side, or until dry. Cool completely and store in an airtight container.