Divide dough into equal parts. Add chocolate and blend until incorporated uniformly. Roll out white dough into a 9 by 12 inch rectangle. Roll out the chocolate dough the same size, and lay over the white dough. Roll up tightly, beginning at the wide end, into a roll 12 inches long and 2 inches in diameter.
Place slices a bit apart on a lightly greased cookie sheet.
Bake 10 to 12 minutes in a 350 degree oven.