Put the graham crackers into a ziplock bag and crush them with a rolling pin till they are in fine pieces (a food processor works too).
Pour the graham cracker dust onto a tiny plate or bowl then dump the hot fudge topping into another small plate or bowl. Take the two cups that you will be serving the milkshakes in and dip the rims into the fudge topping then roll them in the graham cracker dust. Store the cups in the freezer till you are ready to serve.
In a blender combine the marshmallow fluff, milk, and chocolate syrup. Turn it on and run it until the marshmallow fluff has been separated into smaller pieces and not one chunk.
Add the ice cream and turn the blender on till it is combined. If it is too thick for your liking add more milk and if it is too thin add more ice cream.
Pour the milkshake into the cups that have the fudge and graham cracker rim then serve!