Make the Cake Layers

1. Make the chocolate pudding by adding the milk to the powdered pudding mix and whisking for about 2 minutes, until pudding begins to thicken. You can make both packages in one bowl and then divide it in half, or make them in two separate bowls. Set pudding aside.
2. In a large bowl, gently stir the marshmallow fluff and Cool Whip together until well combined.
3. Stir the mini marshmallows into the Cool Whip mixture. Set aside.

Assemble the Cake

1. Place a single layer of graham crackers along the bottom of a 9×13 pan. You may need to break some crackers in half to make them fit.
2. Spread half of the marshmallow mixture on top of the graham crackers.
3. Spread half of the chocolate pudding on top of the marshmallow mixture.
4. Place another layer of graham crackers in a single layer on the top of the pudding.
5. Spread the remaining half of the marshmallow mixture on top of the graham crackers.
6. Spread remaining chocolate pudding on top of the marshmallow mixture.
7. Place another single layer of graham crackers on the top of the pudding.

Finish Off the Cake

1. Spread thick chocolate sauce over the top of the graham crackers.
2. Sprinkle the top of the icebox cake with additional mini marshmallows and a few mini chocolate bars. Refrigerate until ready to serve.
3. If you have a kitchen torch, toast the marshmallows, being careful not to overheat them. Or, place the cake in a toaster oven or your regular oven on the convection oven setting. Watch marshmallows and remove after they begin to brown (about 10 minutes). You can also set your oven to the broiler. Place the cake a few inches below the broiler and watch closely. Remove as soon as the marshmallows look toasted.
4. Serve immediately with a drizzle of chocolate sauce.
5. For the best taste and texture, eat within 3-4 days.