Chocolate Thin Mints

Line a square 8" baking pan with aluminum foil, letting an inch of foil overhang the sides. In a bowl set over barely simmering water or in a microwave oven, heat semisweet chocolate until half the chips are melted. Remove from heat and stir until completely melted and smooth. Spread half the semisweet chocolate evenly in bottom of pan. Refrigerate 5 to 10 minutes. Meanwhile, heat white-chocolate chips until half-melted. Remove from heat and stir until completely melted. Stir in peppermint oil and food coloring until blended. Spread over cooled chocolate. Refrigerate 10 minutes or until firm. Reheat remaining semisweet chocolate if necessary. Spread over cooled white-chocolate layer. Refrigerate until solid. Lift dessert from pan and transfer to cutting board. Peel away foil. With a heavy sharp knife, cut into sixteen 2-inch squares, then cut squares into triangles.