HEAT oven to 400°F.
UNFOLD pastry sheet on lightly floured surface; pierce pastry with fork. Cut pastry crosswise into 3 pieces, following fold lines in pastry. Place in single layer on baking sheet. Bake 15 min. or until golden brown. Cool on wire racks.
MEANWHILE, microwave 4 oz. chocolate and 1/2 cup COOL WHIP in large microwaveable bowl on HIGH 1 min. or until chocolate is almost melted, stirring after 30 sec. Stir until chocolate is completely melted and mixture is well blended. Cool completely, stirring occasionally. Add remaining COOL WHIP; whisk until blended.
SPLIT each pastry piece into 2 layers. Set aside 2 of the top layers. Spread each of the 4 remaining pastry layers with scant 1/2 cup COOL WHIP mixture; top each with 1/3 cup strawberries. Stack 2 of the topped layers; cover with remaining pastry layers. Melt remaining chocolate as directed on package; drizzle evenly over pastry stacks. Refrigerate 4 hours. Cut each stack into 6 pieces to serve.