• Line an 8-inch or 9-inch square baking pan with parchment paper and set it aside. Be sure to let the paper overhang all 4 sides of the pan.

Make the pudding.

• Make the instant vanilla pudding according to the recipe (or box) instructions, transfer it to a large bowl, place plastic wrap directly on top of the pudding and place in the refrigerator to chill for about 1 hour or until cool to the touch.

Make the stabilized whipped cream.

• Bloom the gelatin by placing it and the water in a small, heat-safe bowl, and stirring it gently to combine.
• Allow the mixture to sit at room temperature until the gelatin swells.
• Place the gelatin mixture in the microwave and melt at 60% power for 20 seconds until melted. Set the gelatin aside to cool briefly.
• In the bowl of a stand mixer fitted with the whisk attachment, or a large bowl with a hand mixer, place the chilled cream and sugar, and whisk on medium speed until soft peaks form.
• Add the cooled gelatin, and beat until thickened, about 2 minutes.

Make the filling.

• Remove the cooled pudding from the refrigerator and peel off the plastic wrap.
• Whisk the pudding until smooth and loose with a handheld whisk.
• Add the stabilized whipped cream to the pudding and fold in the cream until it is fully incorporated.
• Set the filling mixture aside.

Assemble the cake.

• Cover the bottom of the prepared pan with graham crackers, breaking them as necessary to evenly cover the surface.
• Top with half of the pudding and whipped cream mixture and spread it into an even layer.
• Place another layer of graham crackers on top of the pudding, top with the remaining pudding mixture and once again spread it into an even layer.
• Finish with a final layer of graham crackers.

Make the ganache and refrigerate the cake.

• In a small, heavy-bottom saucepan, heat the heavy whipping cream until it just begins to simmer.
• Place the chopped chocolate in a medium-size bowl, and pour the hot cream over the chocolate.
• Allow the cream to sit on the chocolate for about a minute, until the chocolate begins to melt, and mix until the chocolate is melted and the mixture is smooth and glossy.
• Pour the warm ganache over the top of the assembled cake, and gently spread it toward the edges of the pan.
• Cover the pan with plastic wrap and place it in the refrigerator to chill for at least 4 hours to allow the filling to set and the graham crackers to soften.
• Place the cake in the freezer for 15 minutes before removing the entire cake from the pan by pulling up on the parchment paper and setting it on a cutting board. That will make the cake a lot easier to slice.
• Using a large, sharp knife, slice the cake into 12 equal squares and serve chilled or frozen.