Microwave chocolate, 2 Tbsp. milk and butter in microwaveable bowl on HIGH 1 to 1-1/2 min. or until butter is melted, stirring every 30 sec. Stir until chocolate is completely melted.
Spread onto bottom of crust. Refrigerate 30 min.; cover with bananas.
Beat pudding mixes and 2 cups milk in large bowl with whisk 2 min.
Let stand 1 min. Stir in 1-1/2 cups COOL WHIP. Spoon over bananas.
Refrigerate 4 hours or until firm. Top with remaining COOL WHIP just before serving.