1 can (14 ounces) sweetened condensed milk, divided
1 cup white baking chips
3 teaspoons peppermint extract
2 to 3 drops green food coloring
In a small saucepan, melt chocolate chips with 3/4 cup condensed milk over low heat, stirring occasionally. Line an 8-in. square dish with waxed paper; butter the paper.
Spread half of melted chocolate mixture into pan; chill for 5-10 minutes (let remaining melted chocolate mixture stand at room temperature).
In another saucepan, melt white baking chips. Stir in remaining condensed milk until smooth. Remove from the heat; add extract and food coloring. Refrigerate until set. Spread over chocolate layer; spread with reserved chocolate mixture. Refrigerate until set. Cut into 1-in. pieces.