Mix instant chocolate pudding with milk and whisk until dissolved. Refrigerate about 10 minutes until firm.
In a mixing bowl, beat together Cool Whip and marshmallow crème fluff until smooth.
Microwave mini marshmallows for 10 seconds to soften, then toast lightly with a kitchen torch if desired, and beat into the Cool Whip mixture.
Line a 9x13 inch pan with foil or parchment paper.
Lay a layer of chocolate graham crackers evenly on the bottom of the pan, filling gaps as needed.
Spread one third of the marshmallow Cool Whip mixture over the cracker layer.
Spread half of the pudding mixture over the marshmallow layer.
Add a layer of regular graham crackers over the pudding, covering evenly.
Spread another third of the marshmallow Cool Whip mixture over the graham crackers, followed by the remaining pudding mixture.
Add a final layer of chocolate graham crackers on top.
Spread the remaining marshmallow Cool Whip mixture over the top layer of chocolate graham crackers.
Use a stand mixer to beat heavy cream on medium-high until bubbly, then add powdered sugar and cocoa powder and beat until stiff peaks form. Adjust sweetness as needed.
Spread the chocolate whipped cream over the top layer.
Refrigerate the entire dessert for 2-4 hours to set.
Optional: Microwave large marshmallows in groups of 10 for 10-15 seconds, transfer to the lasagna, and gently toast with a kitchen torch.
Drizzle with hot fudge sauce and sprinkle leftover graham cracker crumbs before serving.