n a large bowl, vigorously whisk together the instant pudding and milk for 2 minutes. Fold in the whipped topping. Set aside.

Arrange one layer of graham crackers in the bottom of a 9x13-inch baking dish. Do not overlap the crackers, and if necessary, break a few crackers to fill in any gaps.

Top the graham crackers with half of the pudding mixture and carefully spread out into an even layer. Arrange another layer of graham crackers over the pudding. Repeat with the remaining pudding and top with a final, third layer of graham crackers.

Cover with plastic wrap and chill for 1 hour, and up to 24 hours.

To make the ganache, place the chocolate chips in a large bowl. Place the cream and butter in a small saucepan and set the pan over medium heat. Heat the cream until tiny bubbles appears around the edges of the pan, but do not bring the cream to a boil. Pour the cream over the chocolate and let stand for 10 minutes, without stirring. Stir the cream and melted chocolate together until smooth. Pour the ganache over the top layer of graham crackers and gently spread out into an even layer.

Cover with plastic wrap and chill for at least 8 hours or up to 2 days. The longer you chill the cake the better as this gives the graham crackers time to soften.

Slice into squares and serve.

Cover leftovers with plastic wrap and store in the refrigerator for up to 4 days.