Peanut butter and marshmallow is always an awesome pairing, yum! Shake Shack definitely got the perfect ratio of both flavors in this custard flavor. The peanut butter is swirled throughout the custard, and I love how much of it is in each spoonful. Personally, I've never tried a fluffernutter sandwich but I imagine that this is just like it, in deliciously cold ice cream form. This is a flavor that should definitely be on the menu all the time!