How to Make It
Divide Basic Butter Cookie Dough in half. Knead melted unsweetened chocolate into 1 portion until well blended.
Roll each portion into a 12- x 9-inch rectangle on wax paper. Invert chocolate dough onto plain dough; peel off wax paper. Press chocolate dough firmly onto plain dough with a rolling pin. Roll up, in a jellyroll fashion, starting with the long side; cover and chill 1 hour or until firm.
Cut the dough into 1/4-inch slices; place on lightly greased cookie sheets.
Bake at 350˚ for 10 to 12 minutes or until lightly browned. Remove cookies to wire racks to cool.