In a large bowl whisk together the 2 boxes of instant pudding with the 3 cups of cold milk for 2 minutes.

Gently fold in the Cool Whip and set aside.

Line the bottom of a 13x9" baking pan with graham crackers. You will have to break some into smaller pieces to make them fit.

Pour half of the pudding mixture over the graham cracker layer.

Add another layer of graham crackers.

Top that with the rest of the pudding mixture.

Add another layer of graham crackers on top. Set cake aside.

Over medium-low heat in a small sauce pan, whisk together the butter, chocolate chips, sugar, milk, and vanilla. Keep whisking until the chocolate is melted and the sugar is dissolved. Do not boil. After about 5 minutes test to make sure the ganache is smooth and not grainy. If it is grainy, keep whisking.

Once the ganache is smooth, pour it over the top of the cake and use an offset spatula to smooth it out.

Refrigerate at least 6 hours before serving.