Prepare cake batter and bake as directed on package for 2 (9-inch) round layers. Cool cakes in pans 15 min. Pierce cakes with large fork at 1/2-inch intervals.
Add boiling water to gelatin mix; stir 2 min. until completely dissolved.
Pour over cakes. Refrigerate 3 hours.
Heat oven to 350F. Reserve 5 mints for later use.
Place 12 of the remaining mints, about 4 inches apart, on parchment-covered baking sheet.
Bake 5 min. or until mints are melted and each spreads out to 1-1/2- to 2-inch circle. Cool completely before removing from parchment. Meanwhile, repeat with remaining 11 mints.
Melt chocolate as directed on package. Blend 5 reserved mints in blender until finely crushed; place in small bowl. Stir in melted chocolate, sour cream and food coloring.
Dip bottom of 1 cake pan in warm water 10 sec.; unmold onto serving plate.
Spread cake with chocolate mixture. Unmold second cake layer; place on first layer. Frost with COOL WHIP. Refrigerate until ready to serve. Decorate with melted mints.