Lightly grease two cookie sheets; set aside. In a large bowl combine flour, baking powder, salt, and sugar. Make a well in the center of the flour mixture. Place eggs and egg yolks in the well and stir into the flour mixture. Add butter and, if desired, orange peel; stir until dough starts to form a ball. Stir in almonds.
2Turn the dough out onto a lightly floured surface; divide into three equal portions. Shape each portion into a 14-inch-long log. Place logs about 3 inches apart on prepared cookie sheets; flatten logs slightly until about 1-1/2 inches wide. Bake 25 to 30 minutes or until firm and light brown. Remove from oven and place cookie sheets on wire racks; cool 15 minutes.
3Transfer logs to cutting board. Use a serrated knife to cut each roll diagonally into 1/2-inch slices. Place slices, cut sides down, on cookie sheets. Bake for 10 minutes. Turn cookies over; bake 10 to 15 minutes more or until crisp and golden brown. Transfer to a wire racks and let cool.
Makes about 84 cookies.
HAZELNUT BISCOTTI: Prepare as above, except use the option of orange peel and substitute 1 cup chopped hazelnuts for the almonds.
PISTACHIO BISCOTTI: Prepare as above, except use the option of lemon peel and substitute 1 cup chopped pistachios for the almonds.
CASHEW-CHOCOLATE BISCOTTI: Prepare as above except omit the peel and substitute 1/2 chopped cashews and 1/2 cup finely chopped bittersweet chocolate for the almonds.