1 Line 8-inch square pan with foil, allowing foil to extend over sides of pan. Spray with no stick cooking spray. Mix sugar and cocoa powder in large bowl. Set aside.
2 Place butter and 1/4 cup milk in medium microwavable bowl. Microwave on HIGH 1 minute; stir until butter is melted. Stir in vanilla. Add to sugar mixture; mix well. Pour into prepared pan. Refrigerate at least 1 hour or until firm.
3 For the mint layer, place white chocolate chips and 2 tablespoons milk in medium microwavable bowl. Microwave on MEDIUM 1 minute; stir. Microwave additional 15 to 30 seconds, stirring after 15 seconds. Stir in mint extract and green food color. Spread over cooled chocolate layer.
4 Refrigerate 10 to 15 minutes or until firm. Use foil to lift out of pan onto cutting board. Cut into 16 (2-inch) squares. Cut each square diagonally in half, making triangles.