In a large bowl, whisk together the 2 boxes instant vanilla pudding mix and 3 cups cold milk for 2 minutes, until it starts to thicken. Let it sit for 5 minutes to set up.

Gently fold the 8 ounces whipped topping into the pudding until smooth and no streaks remain. This is your éclair filling, light and creamy.

Line the bottom of a 9 by 13 inch dish with a single layer of graham crackers, breaking them to fit and cover the whole surface.

Spread half the pudding mixture evenly over the graham crackers. Top with a second layer of graham crackers.

Spread the remaining pudding mixture over that layer, then finish with a third and final layer of graham crackers on top.

Heat the 1 cup heavy cream in a small saucepan until it just begins to steam and bubble at the edges, then pour it over the 1½ cups chocolate chips in a bowl. Let it sit for 2 minutes, then stir until smooth and glossy. The warm cream is what keeps the chocolate soft and spreadable instead of setting into a hard shell.

Pour the ganache over the top layer of graham crackers and spread it evenly to cover them completely.

Cover and refrigerate for at least 8 hours or overnight. This long chill is not optional, it's what softens the graham crackers into tender cake like layers, which is the whole point of the dish.

Slice into squares and serve cold.