Bakers and confectioners have long known the magic of chocolate combined with mint: Milano Mint Chocolate cookies from Pepperidge Farm, the Girl Scouts' Thin Mints, and Andes Creme de Menthe Thins.

With Valentine's Day approaching, fast-food giant McDonald's is already is chasing the luck of the Irish with a fan-favorite dessert. And Wendy's is giving some competition with a minty treat of its ...