Break up large 1 and 1/2 Hershey bar and place in a large microwave safe bowl. Heat for 30 seconds at a time and stir until chocolate is melted. Remove and set aside.
Add cool whip to melted chocolate and mix until well combined.
Spoon chocolate cool whip into your graham cracker crust, and garnish with remaining 1/2 milk chocolate bar.
Place pie in the refrigerator. Allow to chill for 1-3 hours.