In a large mixing bowl, whisk together the French vanilla pudding mix and 3-1/2 cups of whole milk. Continue whisking until the mixture thickens, which should take about 2 minutes. Once thickened, gently fold in the thawed whipped topping until fully combined.
In your 9x13 inch baking dish, arrange a single layer of honey graham crackers at the bottom. Make sure to cover the entire surface for a solid foundation.
Spread half of the pudding mixture over the layer of graham crackers, smoothing it out with a spatula to create an even layer.
Add another layer of graham crackers on top of the pudding layer, followed by the remaining pudding mixture. Smooth it out again, and finish with a final layer of graham crackers.
In a microwave-safe bowl, combine the milk chocolate chips and heavy cream. Microwave in 30-second intervals, stirring after each, until the chocolate is melted and smooth. Stir in the tablespoon of unsalted butter until fully incorporated.
Pour the chocolate ganache over the top layer of graham crackers, spreading it out evenly with a spatula.
Cover the cake with plastic wrap or aluminum foil and refrigerate for at least 4 hours, or overnight if possible. This will allow the layers to meld together, creating a deliciously cohesive dessert. When ready to serve, slice into squares and enjoy!
