In a large bowl, whisk the instant vanilla pudding mix with the cold milk until the mixture is smooth and begins to thicken.
Gently fold the thawed whipped topping into the pudding mixture until no white streaks remain and the mixture is uniform.
Line the bottom of a 9×13 inch baking dish with a single layer of graham crackers, breaking them if necessary to fit.
Spread one-third of the pudding mixture evenly over the graham cracker base.
Repeat the layering process (crackers, then pudding) until all ingredients are used, ensuring you finish with a layer of graham crackers on top.
In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer.
Place the chocolate chips in a heat-resistant bowl and pour the hot cream directly over them.
Stir the mixture steadily until the chocolate is fully melted and the ganache becomes smooth and glossy.
Pour the finished ganache over the top layer of crackers, using a spatula to smooth it into an even coating.
Cover the dish and refrigerate for at least 8 hours, or overnight, to allow the crackers to soften and the layers to set.