Mix the pudding mix and milk together per the package directions.
Whip 1 cup heavy cream with the powdered sugar and vanilla until stiff peaks form but do not over whip. Fold the cream into the pudding after the pudding has set.
Pour the chocolate chips into a heat-safe bowl. Heat the remaining 1 cup of cream over medium heat until it just begins to come to a boil. Pour the heated cream over the chocolate chips and let stand for 5 minutes. Add the butter and stir until the butter has melted and the mixture is smooth and glossy.
Spray a 9x12-inch baking dish with cooking spray. Place a layer of graham style crackers in the bottom of the baking dish, breaking pieces if needed to fully cover. Top with half the pudding/cream mixture. Top with another layer of crackers then the rest of the pudding/cream mixture then another layer of crackers. Pour the chocolate mixture over the top and smooth into an even layer. Refrigerate for at least 4 hours, preferably overnight.