In a large bowl whisk together cold milk and instant pudding mix until thickened.
Fold in whipped topping until smooth and fully combined.
Arrange a single layer of graham crackers in the bottom of a 9x13-inch dish.
Spread half of the pudding mixture evenly over the crackers.
Add another layer of graham crackers on top.
Spread remaining pudding mixture over the second cracker layer.
Finish with a final layer of graham crackers.
Microwave chocolate frosting for 15–20 seconds to soften, then spread evenly over the top.
Cover and refrigerate for at least 8 hours or overnight before serving.