This little sweet potato casserole is the kind of dish that shows up at church potlucks and Sunday suppers and disappears before the ham is even carved. My aunt first brought it to our table one Easter, in a simple glass baking dish, the top all puffed and golden with gooey marshmallows. We all assumed she’d fussed with cream and spices and who-knows-what, and she just laughed and said, “Three ingredients, that’s it.” It’s the kind of old-fashioned Midwestern comfort food that tastes like it took all afternoon, but really just leans on sweet potatoes, butter, and marshmallows to do the work. If you need something cozy, crowd-pleasing, and almost embarrassingly easy, this is it.
Serve this sweet potato casserole warm, right out of the glass baking dish, alongside baked ham, roasted turkey, or a simple meatloaf. It’s lovely with green beans, a crisp lettuce salad, or buttered corn to balance the sweetness. For a holiday table, it fits right in with stuffing, rolls, and cranberry sauce. For a simple Sunday supper, pair it with sliced ham steaks or pork chops and a pan of biscuits, and let it play the role of both side dish and dessert.
3-Ingredient Sweet Potato CasseroleServings: 6-8
Ingredients
3 pounds sweet potatoes (about 4–5 medium), peeled and cut into chunks
4 tablespoons unsalted butter, plus more for greasing the dish
3 cups mini marshmallows
Directions
Preheat your oven to 375°F (190°C). Lightly butter a 2-quart glass baking dish (an 8x8-inch or similar size works well) so the potatoes don’t stick.
Place the peeled, chunked sweet potatoes in a large pot and cover them with cold water by about 1 inch. Set the pot over medium-high heat and bring to a boil. Once boiling, reduce the heat slightly and simmer until the sweet potatoes are very tender when pierced with a fork, about 15–20 minutes.
Drain the sweet potatoes well in a colander, shaking gently to remove excess water. Return the hot sweet potatoes to the empty pot.
Add the 4 tablespoons of butter to the hot sweet potatoes. Using a potato masher or sturdy fork, mash until mostly smooth and the butter is fully melted and mixed in. Taste and, if you like, add a small pinch of salt (optional and not required for the basic 3-ingredient version).
Spoon the mashed sweet potatoes into the prepared glass baking dish and spread them into an even layer, smoothing the top with the back of a spoon.
Sprinkle the mini marshmallows evenly over the surface of the mashed sweet potatoes, covering the top from corner to corner so you get a gooey layer in every scoop.
Place the baking dish on the center rack of the preheated oven and bake for 12–18 minutes, or until the marshmallows are puffed and turning a light golden brown on top. Keep an eye on them during the last few minutes, as marshmallows can go from toasted to burned quickly.
If you prefer a deeper toast on the marshmallows, you can switch the oven to broil for 1–2 minutes at the very end. Watch closely and remove the dish as soon as the marshmallows are evenly browned.
Carefully remove the casserole from the oven and let it sit for about 5–10 minutes before serving. The marshmallow topping will be very hot and molten at first; a short rest helps it set just enough while still staying gooey.
Serve warm, scooping down through the toasted marshmallows into the mashed sweet potatoes so each serving has a bit of both layers.
Variations & Tips
You can dress this up in small ways without losing the spirit of the original three-ingredient recipe. If you like a little spice, mash in a teaspoon of ground cinnamon or pumpkin pie spice with the butter. For extra richness, add a splash of cream or milk when mashing the sweet potatoes. A drizzle of maple syrup or a spoonful of brown sugar can deepen the sweetness if your potatoes are on the mild side. If you don’t have mini marshmallows, you can use regular-size marshmallows and tear them in half before scattering over the top. For a slightly less sweet version, use fewer marshmallows and leave some of the potato showing through. To make this ahead, you can boil and mash the sweet potatoes with butter, spread them in the dish, cover, and refrigerate for up to 24 hours. When ready to serve, let the dish sit at room temperature while the oven heats, then top with marshmallows and bake, adding a few extra minutes if needed so the center is hot. Food safety tips: Always refrigerate leftovers within 2 hours of baking, and store them in a covered container in the refrigerator for up to 3–4 days. Reheat leftovers in a 325°F (165°C) oven until hot in the center; avoid leaving the casserole out at room temperature for long periods, especially on warm days or crowded holiday tables. When boiling and draining the sweet potatoes, handle the pot and hot water carefully to avoid burns, and keep children and pets clear of the stove area.
