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.