- 6 large sweet potatoes, peeled and cut into chunks
- 1 cup white sugar
- 1/2 cup brown sugar
- 2 tablespoons ground cinnamon
- 1 tablespoon butter, softened
- miniature marshmallows, or as needed
- Place sweet potatoes in a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 20 minutes; drain.
- Preheat oven to 375 degrees F (190 degrees C). Grease a deep casserole dish with butter.
- Mash potatoes with a potato masher in a bowl until no large lumps remain. Stir white sugar, brown sugar, cinnamon, and butter into the mashed sweet potatoes; transfer to prepared casserole dish. Cover sweet potato mixture with a layer of miniature marshmallows.
- Bake in preheated oven until marshmallows are browned, about 30 minutes.