Line a 13x9x2″ baking dish with graham crackers in a single layer.
Whisk the milk and vanilla pudding together until well blended. Gently fold in the Cool Whip. Spread half the Cool Whip mixture over the graham crackers in the dish. Add another layer of graham crackers. Spread the remaining Cool Whip mixture over. Now top with one last layer of graham crackers.
Remove the foil and cover from the frosting and microwave for 20-40 seconds until not quite melted – to an almost-glaze-consistency. Start at 20 seconds and stir, re-heating as needed.
Stir, then pour the frosting over the last graham cracker layer.
Cover and chill until set, usually a couple of hours or overnight.