Preheat your oven to 350 degrees and line a deep dish 9 inch pie pan with your pie crust.
Whisk together the potato and melted butter. Then stir in all the remaining ingredients except the marshmallows. Pour it into the pie crust and bake for 40 to 45 minutes, until the edges are set but the middle has a little jiggle still too it.
Take the pie out and dot it with the marshmallows. Turn on your broiler and put the pie back in, watching very closely. Broil until the marshmallows turn brown on top, about five minutes. When you take the pie out, the marshmallows will be standing up still all weird, but as the pie cools they will fall and make a nice toasted marshmallow layer.
Let cool on the counter for a half hour and then completely in the refrigerator overnight.