Whisk pudding mix with cold milk until thickened.
Fold in whipped topping gently until smooth and fluffy.
Place a layer of graham crackers in a baking dish.
Spread half of the pudding mixture evenly over crackers.
Add another layer of graham crackers and spread remaining pudding.
Top with a final layer of graham crackers.
Warm chocolate frosting slightly and spread evenly on top.
Chill for at least 6 hours or overnight until layers soften.
Slice into squares and garnish with chocolate shavings or berries if desired.