PREPARE cake batter and bake as directed on package for two 9-inch round cake layers. Cool cakes in pans 15 min. Pierce cakes with large fork at 1/2-inch intervals. Stir boiling water into dry jelly powder 2 min. until completely dissolved. Pour over cakes. Refrigerate 3 hours.

HEAT oven to 350ºF. Crush 5 mints in blender; mix with melted chocolate, sour cream and food colouring. Place 1/2 the remaining mints, about 4 inches apart, on baking sheet covered with parchment paper. Bake 5 min. or until mints melt to form 2-1/2- to 3-inch circles. Cool before removing from baking sheet. Repeat with remaining mints.

DIP bottom of 1 cake pan in warm water 10 sec.; unmould onto plate. Spread with chocolate mixture. Unmould second cake; place on first layer. Frost with Cool Whip. Refrigerate until ready to serve. Decorate with melted mints.