In a medium bowl beat margarine or butter on medium speed with an electric mixer for 30 seconds. Add sugar, baking powder, and baking soda; beat until combined. Beat in egg product and vanilla. In a small bowl stir together flour and coca powder; beat as much of the flour mixture as you can into the margarine mixture. Stir in the remaining flour mixture and cherries.
On waxed paper; shape dough into two 12-inch-long logs. Place on prepared cookie sheet; flatten the logs slightly to 1 1/2-inch width. Bake in a 375 degree F oven for 18 to 20 minutes or until firm and a wooden toothpick inserted near center of each log comes out clean. Cool on sheet for 1 hour.
Cut each log into 1/2-inch slices. Arrange the slices, cut sides down, on the cookie sheet. Bake in 325 degree F oven for 8 minutes; turn and bake for 8 minutes more or until crisp. Transfer cookies to a wire rack. Makes 40 cookies.
If desired, in a small microwave-safe bowl combine chocolate pieces and shortening. Microwave on 50 percent power (medium) for 1 to 2 minutes or until melted and smooth, stirring twice. Dip one end of each biscotti into melted chocolate. Let stand until chocolate is set.