Divide both doughs in half. Roll one portion of Chocolate-Cinnamon Dough into a 9" square on a lightly floured surface. Roll one portion of Vanilla Dough into a 9" square, and place on top of chocolate square. Continue rolling and stacking remaining two portions of dough, resulting in a 4-layer stack of alternating dough, pressing layers firmly to adhere.
Tear away a portion of stacked dough, and knead 2 or 3 times. (Too much kneading will prevent marbled look.) Roll dough to 1/8" thickness on a lightly floured surface. Cut with a 3" heart-shaped cookie cutter; place on ungreased cookie sheets. Repeat procedure with remaining dough.
Bake at 350° for 12 minutes or until lightly browned. Cool 1 minute on cookie sheets; remove to wire racks, and cool completely.