In heavy saucepan, over low heat, melt chocolate chips with 1 cup sweetened condensed milk; add vanilla. Spread half the mixture into wax-paper-lined 8- or 9-inch square pan; chill 10 minutes or until firm. Hold remaining chocolate mixture at room temperature.
In heavy saucepan, over low heat, melt white confectioners coating with remaining sweetened condensed milk (mixture will be thick). Add peppermint extract and food coloring (optional).
Spread on chilled chocolate layer; chill 10 minutes longer or until firm.
Spread reserved chocolate mixture on mint layer. Chill 2 hours or until firm. Turn onto cutting board; peel off paper and cut into squares. Store leftovers covered in refrigerator.