Remove foil lid from cake package. (Do not remove cake from pan.) Pierce cake with skewer at 1/2-inch intervals, poking skewer through cake to bottom of pan.

Add boiling water to gelatin mix in small bowl; stir 2 min. until completely dissolved. Stir in cold water; pour over cake. Refrigerate 1 hour. Meanwhile, make curls from semi-sweet chocolate.

Microwave chocolate on HIGH a few seconds to warm it slightly. Draw vegetable peeler slowly over flat bottom of chocolate to form thin curls. Place on waxed paper-covered plate. Refrigerate until ready to use.

Invert cake onto platter. Cut cake horizontally in half. Spread bottom half of cake with 1/3 cup COOL WHIP; cover with 1 cup pie filling and top cake layer. Frost top and sides of cake with remaining COOL WHIP. Garnish with remaining pie filling and chocolate curls.

Dessert can be prepared ahead of time. Refrigerate up to 12 hours before serving.