1. In a large bowl, combine the flour, sugar, cocoa, and baking powder, and stir to mix well. Add the almonds if desired, and stir to mix. Add the remaining ingredients, and stir just until the dough holds together.
2. Turn the dough onto a lightly floured surface, and shape into two 8-x-2-inch logs. (If the dough is too sticky to handle, knead in a little more flour.) Coat a baking sheet with nonstick cooking spray, and place the logs on the sheet. Bake at 350 °F for about 23 minutes, or until lightly browned. Transfer the logs to a wire rack, and allow to cool for 10 minutes.
3. Place the logs on a cutting board, and use a serrated knife to slice the logs diagonally into 1/2-inch-thick slices. Place the slices on a baking sheet, and bake at 300 °F for 20 minutes, or until lightly browned, turning after 10 minutes.
4. Transfer the biscotti to wire racks, and cool completely.