To start we mixed the semisweet and milk chocolate chips in a bowl and microwaved it until it melts. Then we pulled out about 12 standard muffin tin paper liners and spooned the melted chocolate mix into the bottom of the liners. About 1/4 inch of chocolate works just fine. Use a spoon to spread the chocolate a little up the sides of the liner. We then put the tins into the fridge to allow the chocolate to solidify (about 10 minutes). While the chocolate liners are solidifying in the fridge, mix together the peanut butter, graham cracker crumbs, powdered sugar and pinch of salt in a bowl. Make sure the peanut butter mixture is smooth. Spoon the peanut butter on top of the solidified chocolate, right in the middle.
Take about a tablespoon of marshmallow fluff and gently place it on top of the peanut butter. Marshmallow fluff naturally flattens out and runs at room temperature so let these sit for 5-10 minutes so the marshmallow flattens out a bit on top of the peanut butter.
Once this happens, put your leftover chocolate chip mixture back into the microwave to get it soft again. Then spoon the chocolate on top of the marshmallow allowing it to run down the sides of the marshmallow and connect with the chocolate on the bottom and sides.
Put the whole Fluffernutter cup back in the fridge to allow the chocolate to set once again (about 10 more minutes). Serve and enjoy!