Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets.
In a large bowl, cream together the sugar, margarine and olive oil until smooth. Stir in the vanilla and egg substitute.
Combine the flour, cocoa, and baking powder. Stir into the creamed mixture. Fold in the chocolate pieces. Cover, and chill dough for 10 minutes.
Divide the dough into two equal pieces.
Roll each piece into a log about 9 inches long.
Place the logs onto the prepared cookie sheets about 4 inches apart. Flatten each one down to 1 inch thickness.
Bake in the preheated oven for 20 to 25 minutes, or until firm. Cool on sheets for 15 minutes before removing to wire racks to cool completely.
Move the cookie loaves to a cutting board. Using a serrated knife, slice each loaf crosswise into 3/4 inch slices. Return slices to the baking sheet cut side down and bake for an additional 8 to 10 minutes on each side, until dry and lightly toasted. Cool completely before storing in an airtight container.
