In a high power blender, combine milk, hot fudge, marshmallows, graham crackers, and espresso (if using). Blend on a low speed for just a few seconds until mixed.
Add in ice cubes and blend until smooth.
(Optional) Serve topped with whipped cream or marshmallow cream for extra ridiculous goodness.
Video
Notes
Coffee lovers: add 1 teaspoon espresso powder for a coffee flavored s'mores dessert