Sweet Potato Casserole with Marshmallows
This sweet potato casserole with marshmallows is pure Thanksgiving nostalgia: fluffy, buttery sweet potatoes whipped with brown sugar, vanilla, and a whisper of cinnamon, baked under a thick blanket of marshmallows that puff up and toast to a golden, gooey top. It walks the line between side dish and dessert in the best possible way, and it is usually the first bowl scraped clean.
It is also wonderfully low-stress. The sweet potatoes can be boiled and mashed ahead, the casserole assembles in minutes, and the marshmallows go on at the very end — so the topping is always freshly toasted, never soggy, when it reaches the table.
This recipe is part of our Thanksgiving collection — the turkey, every classic side, the pies, and a day-by-day plan for getting it all to the table.
Prep time: 20 minutes Cook time: 45 minutes Servings: 8
What You’ll Need
- Large mixing bowl
- Potato masher or hand mixer
- Large pot
- Colander
- 9×13-inch baking dish
- Rubber spatula
For bowls that make mashing and mixing easy, see our best mixing bowls guide.
Ingredients
- 3 pounds sweet potatoes (about 4 large), peeled and cut into 1-inch chunks
- 1/2 cup (1 stick) unsalted butter, melted
- 1/2 cup packed light brown sugar
- 2 large eggs, lightly beaten
- 1/2 cup whole milk
- 1 teaspoon pure vanilla extract
- 1/2 teaspoon ground cinnamon
- 1/4 teaspoon ground nutmeg
- 1/2 teaspoon fine sea salt
- 3 cups mini marshmallows (about one 10-ounce bag)
Instructions
- Boil the sweet potatoes. Place the sweet potato chunks in a large pot, cover with cold water by about an inch, and bring to a boil. Cook for 15–20 minutes, until completely tender when pierced with a fork. Drain well and return to the pot.
- Mash until smooth. Mash the sweet potatoes with a potato masher until mostly smooth — a few small lumps are fine and add texture. Stir in the melted butter and brown sugar until combined.
- Add the remaining filling ingredients. Stir in the beaten eggs, milk, vanilla, cinnamon, nutmeg, and salt. Mix until the filling is smooth, fluffy, and evenly combined.
- Spread into the dish. Transfer the sweet potato mixture to a greased 9×13-inch baking dish and smooth the top with a rubber spatula.
- Bake the base. Bake at 350°F (175°C) for 25 minutes, until the edges are just beginning to set and the surface looks matte rather than wet.
- Add the marshmallows. Remove the dish from the oven and scatter the mini marshmallows evenly over the top, covering the surface completely.
- Toast until golden. Return the dish to the oven and bake for 10–12 minutes more, until the marshmallows are puffed and golden brown. Watch closely in the final minutes — marshmallows go from golden to burnt fast.
- Rest and serve. Let the casserole rest for 5–10 minutes before serving so it firms up slightly and scoops cleanly. Serve warm.
Tips for the Best Sweet Potato Casserole with Marshmallows
- Drain the potatoes thoroughly. Water left clinging to the boiled sweet potatoes makes a loose, soupy casserole. Drain well, then return the pot to low heat for a minute to steam off any remaining moisture before mashing.
- Do not walk away during the marshmallow stage. Marshmallows toast in minutes and burn in seconds, especially under a hot oven element. Stay nearby and pull the dish the moment the tops are evenly golden.
- Make it ahead — but add the marshmallows fresh. Assemble the sweet potato base up to two days in advance, cover, and refrigerate. On Thanksgiving Day, bake the base as directed, then add the marshmallows and toast just before serving so the topping is always gooey and golden.
Buttery, sweet, and crowned with toasted marshmallows — this is the Thanksgiving side dish that tastes like childhood, and it never lasts long on the table.
Serve it alongside the creamiest mashed potatoes, and plan the rest of the dessert table with our Thanksgiving desserts roundup.
Frequently Asked Questions
Can I assemble sweet potato casserole ahead of time?
Yes — assemble the base up to two days ahead, cover and refrigerate. Hold the marshmallows back until baking day; they go on for the last 10 minutes so they toast instead of steaming.
Can I use a pecan topping instead of marshmallows?
Absolutely — a brown-sugar and pecan streusel is the other classic. Scatter it over the base before baking rather than at the end, and bake until the casserole is bubbling at the edges.
How do I reheat leftovers?
Covered at 325°F (165°C) for 20–25 minutes, until hot through. If the marshmallow top has gone flat, two minutes under a hot grill at the end brings back the toast — watch it constantly, marshmallows colour in seconds.
