Line a 9x13 pan with parchment paper and the parchment paper to hang up the sides.
In a large bowl make the instant pudding with the milk. Pour the pudding into the casserole dish and spread evenly. Place into the freezer to chill while making the marshmallow layer.
In another large bowl beat the cream cheese with a hand mixer. Add the marshmallow fluff and beat again until combined. Fold in the whipped topping.
Use a rubber spatula to top the chocolate pudding with the marshmallow mix and spread evenly into a layer. Return to freezer for 4-24 hours.
Once frozen, remove the layers from the casserole dish and place onto a cutting board. Allow to sit for 10 minutes.
Break the graham crackers in half and place onto the layers. Use a hot, sharp knife to cut around the graham crackers and trim the edges of excess chocolate and marshmallow.
Use another cutting board or a sheet pan to flip the sandwiches over and top the other side.
Enjoy immediately or allow the filing to melt slightly so the graham crackers really stick.
The recipe card indicates you will need 24 hours of chill time in the freezer. This isn't entirely necessary, however, you will need a minimum of 4-6 hours to freeze the pudding and marshmallow fluff layers. This can be made the morning of your plans.
You can also make these frozen s'mores 24 hours in advance. Keep in the freezer and allow them to thaw for 20 minutes before enjoying. If you want to make them further in advance, follow the instructions for the filling layer (pudding and fluff), freeze, then cut the filling into squares. Keep this frozen until ready to serve. When ready, take the filling out of the freezer then place the graham crackers onto them. This will help keep the graham crackers fresh as they tend to get soft when kept in the freezer. Let the graham crackers rest on the filling layer for 20 minutes before enjoying, allowing the crackers to adhere to the filling.