Preheat oven to 400 degrees F.
Go ahead and use the peelings as the crust, but cook them first: Scrub potatoes and pat dry. Peel potato and lay peelings evenly in the bottom of a 9-inch pie pan. Place in oven and cook for about 15-20 minutes, because it would be nice if they were a little crispy. When they’re done, reduce oven heat to 350 degrees F.
In the meantime, place potatoes in a large pot, cover with salted water, and boil until they’re soft, however long that takes (about 30-40 minutes). Then, drain the potatoes and mash them up with the butter until they’re nice and fluffy. Add milk slowly and stir until milk is absorbed. Stir in that delicious cheese and the sour cream, too, if you want it (and who wouldn’t?).
Pour the potato mixture on top of the crispy skins. Then, put the pie in the oven for about 30 minutes until it’s all melty and glorious (and lightly browned). Allow to cool for about 15 minutes, until it sets. Serve warm. To reheat: Cover with foil and heat for 15-20 minutes in an oven preheated to 300 degrees F.