Microwave 2 cups of the marshmallows and 2 Tbsp.milk in medium microwavable bowl on HIGH 45 seconds; stir gently. (Marshmallows will be partially melted.) Refrigerate 15 minutes to cool.
Add 1 cup of the whipped topping; stir with wire whisk until well blended. Stir in remaining 1/2 cup marshmallows.
Pour 2 cups milk into large bowl. Add dry pudding mixes. Beat with wire whisk 2 minutes or until well blended. (Mixture will be thick.) Gently stir in remaining 1-1/2 cups whipped topping. Spoon into crust. Spread marshmallow mixture over pudding layer. Drizzle with melted chocolate. Refrigerate 4 hours or until set. Store leftover pie in refrigerator.