Step 1

Preheat oven to 350°F. Spray 13x9-inch pan with cooking spray. In medium bowl, stir together marshmallow creme, mint extract and 4 drops of the food color until light green.

Step 2

In large bowl, make brownie mix as directed on box, using water, oil, and eggs. Spread batter in pan. Drop 4 or 5 large tablespoonfuls of marshmallow mixture onto batter (reserve remaining marshmallow mixture). Gently pull table knife through marshmallow mixture and batter in S-shaped curves in continuous motion for marbled design. Spread evenly in pan.

Step 3

Bake 25 to 28 minutes or until set. Cool completely, about 1 hour.

Step 4

In small microwavable bowl, microwave chocolate chips on High 30 seconds; stir. Microwave 30 seconds longer; stir until smooth. Stir melted chips and frosting into remaining marshmallow mixture. Stir in remaining 4 drops food color until light green; spread over cooled bars. Sprinkle with cookies; press in slightly. Cut into bars.