Side Dishes
This sweet potato casserole recipe with marshmallows and streusel topping transforms humble sweet potatoes into a showstopping side dish that's crispy, creamy, and irresistibly gooey.
The secret lies in the perfect balance of spiced sweet potatoes, a buttery streusel topping, and just the right amount of marshmallows that melt into golden rivers when baked. I developed this recipe during a holiday gathering when I wanted something that would impress without requiring hours in the kitchen.
The foundation starts with perfectly spiced sweet potatoes—sweet, tender, and just the right texture—before being topped with a crumbly streusel that adds a delightful contrast. The marshmallows, strategically placed, create that signature caramelized top that's impossible to resist.
What makes this recipe truly special is how it combines simplicity with restaurant-quality results, using just a few key ingredients and a single baking dish.
By the time it emerges from the oven, you'll have a casserole with a crispy streusel crust, tender sweet potatoes, and marshmallows that have melted into glossy, golden pools.
The aroma alone will have everyone gathering around the table, and each bite delivers a perfect harmony of textures—creamy, crispy, and sweet all at once.
This casserole is equally at home on Thanksgiving tables or as a comforting weeknight dinner. The recipe scales easily, making it perfect for feeding a crowd or prepping ahead for meal prep. Here's how to create this crowd-pleasing classic that's sure to become a family favorite.
Ingredients for sweet potato casserole recipe with marshmallows and streusel topping
Sweet, spiced, and topped with golden marshmallow rivers—this casserole delivers restaurant magic with just 14 ingredients.
| Ingredient | Amount | Notes |
|---|---|---|
| Large Sweet Potatoes 🍠 | 2 ½ lbs | Peeled and cubed evenly (1.5-inch pieces) |
| Unsalted Butter 🧈 | ¾ cup | Cold, cut into small cubes |
| Light Brown Sugar 🍚 | 1 cup | Packed firmly for accuracy |
| All-Purpose Flour 🌾 | 1 ½ cups | Sifted for light streusel |
| Cinnamon Sticks 🌿 | 2 whole | Or 2 tsp ground cinnamon |
| Ground Nutmeg 🌶️ | ½ tsp | Freshly grated preferred |
| Salt 🧂 | ½ tsp | Diamond Crystal preferred |
| Large Eggs 🥚 | 2 whole | Room temperature for even bake |
| Mini Marshmallows 🍬 | 3 cups | Kraft brand for classic texture |
| Granulated Sugar 🍚 | ½ cup | For marshmallow topping |
| Vanilla Extract 🥛 | 1 tsp | Pure Madagascar preferred |
| Heavy Cream 🥛 | ½ cup | Full-fat for richness |
| Ground Ginger 🌶️ | ¼ tsp | Freshly ground for warmth |
| Chopped Walnuts 🥜 | ½ cup | Toasted for nutty depth |
The sweet potatoes are your foundation—orange-fleshed, firm varieties like Beauregard work best. Trader Joe's has them pre-peeled for convenience, but fresh is ideal. For the streusel, cold butter creates flaky layers, and light brown sugar adds moisture without over-sweetening. The cinnamon sticks infuse subtle warmth (or swap for ground if you're impatient). Toast your walnuts in a dry pan for 3-4 minutes—they'll smell incredible and add serious texture. Pro tip: Use a mandoline for even cubes if you're feeling fancy.
No marshmallows? Mini meringue nests work in a pinch, though they won't caramelize the same way. Swap brown sugar for coconut sugar if you're watching refined sugar, but expect slightly denser streusel. The streusel can go in the fridge for 3 days or frozen for 3 months—just let it sit at room temp before adding to the casserole. For extra richness, replace half the heavy cream with mascarpone cheese. And if you're feeling adventurous, add 1/4 tsp cardamom to the streusel for a Middle Eastern twist.
This casserole reheats beautifully—350°F for 15-20 minutes until bubbly. Make ahead? Assemble completely (minus marshmallows), cover with foil, and bake at 350°F for 45 minutes before adding the marshmallow layer. Store leftovers in the fridge for 4 days—the streusel stays crispy, and the marshmallows firm up nicely. For serving, sprinkle with flaky sea salt and extra cinnamon. The golden rivers? That's your sign it's ready—no need to rush it out of the oven.
Why You'll Love This Recipe
- One-Pan Magic: I swear by this recipe—just peel, cube, and roast. The cinnamon sticks infuse the sweet potatoes while you mix the streusel and toast the marshmallows, all in the same dish. Zero cleanup, maximum flavor.
- Streusel That Sticks: That buttery brown sugar streusel? It’s the star. It clumps just enough to hold its shape but melts into a caramelized blanket when broiled—like a hug for your sweet potatoes. (Yes, even my picky husband licks the plate.)
- Holiday Ready (But Not Just Then): I make this for Thanksgiving, but honestly? It’s my go-to for Sunday dinners, potlucks, or when I need a crowd-pleaser that doesn’t scream “holiday.” The marshmallows puff up golden under the broiler—no one can resist that.
- Budget-Friendly Leftovers: Sweet potatoes and flour stretch far, and the leftovers reheat like a dream. I’ll be real: I’ve microwaved cold slices straight from the fridge for breakfast (don’t judge). Plus, it’s cheaper than buying a store-bought casserole—same taste, better texture.
Step-by-step instructions for sweet potato casserole with marshmallow streusel
Here's how to create that perfect balance of gooey marshmallow rivers and buttery streusel crust.
Prepare the Sweet Potato Base
Preheat your oven to 375°F and line a 9x13-inch baking dish with parchment paper. Peel and cube the 2.5 lbs large sweet potatoes into 1.5-inch pieces for even cooking. Spread them in a single layer on a baking sheet and roast for 20-25 minutes until tender when pierced with a fork.
While they roast, reduce the oven temperature to 350°F for the final bake. The sweet potatoes should be soft enough to mash easily but not falling apart. Once cooled slightly, transfer them to a mixing bowl and mash until smooth, leaving some texture for better texture in the final casserole.
Make the Marshmallow Topping
In a medium bowl, combine the 3 cups mini marshmallows, 0.5 cup granulated sugar, and 0.5 cup heavy cream. Microwave on high for 45-60 seconds until the marshmallows are just melted and the mixture is smooth but not bubbling. Stir well to create a glossy, pourable topping.
This is the moment that matters: the topping should be thick enough to cling to the sweet potatoes but still flow slightly when poured. If it's too stiff, microwave for 10-second intervals until perfect. Set aside while you prepare the streusel topping.
Create the Streusel Topping
In a large bowl, cut the 0.75 cup unsalted butter into small cubes and use a pastry cutter or fork to work it into the 1.5 cups all-purpose flour until crumbly. Add the 1 cup light brown sugar, 0.5 tsp salt, 0.5 tsp ground nutmeg, 0.25 tsp ground ginger, and break the 2 whole cinnamon sticks into small pieces, adding them to the mixture.
Mix until the streusel reaches a sandy, crumbly consistency with some larger pieces remaining. This texture ensures a perfect balance of crispy and crumbly streusel. If the mixture seems too dry, add 1 tablespoon cold water to help bind it together.
Assemble and Bake to Perfection
Transfer the mashed sweet potatoes to your prepared baking dish and spread them evenly. Pour the marshmallow mixture over the top, creating a thick layer that will melt into golden rivers. Sprinkle the streusel topping evenly over the marshmallows, pressing down gently to help it adhere.
Bake for 30-35 minutes until the edges of the streusel are golden brown and the marshmallow topping is bubbling and beginning to caramelize. The center should still be slightly soft to the touch. Remove from the oven and let it rest for 10 minutes before serving.
Add Walnuts and Serve Warm
Just before serving, sprinkle the 0.5 cup chopped walnuts evenly over the top of the casserole. The walnuts add a delightful crunch that contrasts beautifully with the soft sweet potatoes and gooey marshmallows. Serve warm with a dollop of whipped cream or vanilla ice cream for the ultimate indulgence.
Here's the thing—this casserole tastes even better the next day when the flavors have melded together. The marshmallows will have fully melted into golden rivers, and the streusel will be perfectly crisp. Enjoy this comforting classic that's perfect for holiday gatherings or family dinners!
Pro Tips For Making Sweet Potato Casserole Recipe With Marshmallows And Streusel Topping
- Peel and Cube Evenly: Sweet potatoes should be cut into 1-inch cubes—not too big, not too small. I learned this the hard way: big chunks stay undercooked, while tiny ones burn before the center softens. Use a knife with a serrated edge for cleaner cuts, and don’t skip rinsing the cubes after cutting—it removes excess starch and prevents gummy texture.
- Boil Until Fork-Tender: Sweet potatoes are done when they’re soft enough to pierce with a fork but still hold shape—no mush. I used to pull them out too soon, and the casserole ended up dry. Boil for 10-12 minutes (not 5), then drain well. Cold potatoes mash better and won’t turn to glue in the oven.
- Toast the Streusel Dry: The streusel topping is where flavor hides, but it’ll turn greasy if the butter’s not crisp. Mix cold butter into the flour-sugar-cinnamon mix, then rub it between your fingers until it resembles coarse crumbs—no wet dough. Sprinkle it over the casserole after the marshmallows go on, so it stays golden, not soggy.
- Bake Low and Slow: Crank the oven to 350°F (not 375°F) and bake covered with foil for the first 20 minutes. This lets the marshmallows puff without burning while the streusel sets. After uncovering, watch closely—marshmallows go from golden to charred in 5 minutes. If yours look done too fast, reduce heat to 325°F and bake longer.
Essential equipment for perfect results
Baking Dish Essentials
Start with a 9x13-inch baking dish—this size is perfect for even heat distribution and creates the ideal surface area for the marshmallow rivers to form.
I recommend using dark-colored aluminum (like Calphalon) for better browning, but glass works too. Line it with parchment paper for easy removal and cleanup. 🍠
Mixing Tools
A pastry cutter or sturdy fork is essential for creating the streusel topping—it helps distribute the cold butter evenly into the flour for that perfect crumbly texture. For the marshmallow mixture, a microwave-safe bowl is a must, and I prefer a medium-sized glass bowl (like Pyrex) for even heating.
A rubber spatula comes in handy for scraping every last bit of that gooey mixture.
Measuring Precision
Accurate measurements are key, especially for the streusel. Use a liquid measuring cup for the brown sugar and heavy cream, and a dry measuring cup with a level scoop for the flour.
For the marshmallows, a standard 1-cup dry measure works best—pack them lightly to avoid overfilling. A microplane for fresh nutmeg and a small knife for chopping cinnamon sticks complete the toolkit.
Optional Pro Tools
For extra precision, a mandoline slicer makes quick work of even sweet potato cubes, while a digital kitchen scale ensures perfect butter-to-flour ratios. If you're making this ahead, a vacuum sealer preserves freshness for up to 3 months in the freezer.
And trust me, a fine-mesh sieve helps sift the flour for a lighter streusel texture—worth the investment if you make this often. ✨
Serving Essentials
Don’t forget serving tools! A long-handled spatula helps transfer the casserole from oven to table safely, and a small offset spatula perfects the marshmallow drizzle. For presentation, a flaky sea salt shaker and mini cinnamon sticks elevate the dish instantly.
Serve with whipped cream in a small squeeze bottle for easy topping at the table.
Nutrition facts
Frequently asked questions
Can I make this casserole ahead of time?
Assemble everything except the marshmallow topping, cover tightly with foil, and refrigerate for up to 24 hours. When ready to bake, add the marshmallows and bake as directed. For make-ahead baking, assemble completely (including marshmallows), cover with foil, and bake at 350°F for 45 minutes before adding any final toppings. The flavors meld beautifully overnight!
What if my marshmallow topping isn't melting properly?
This usually happens if the mixture was microwaved too long or wasn't hot enough when poured. For next time, microwave in 10-second bursts until just melted, then stir immediately. If it's already in the oven, cover loosely with foil for 5-10 minutes to help it melt evenly. The key is patience—those golden rivers need time to form!
Can I substitute regular marshmallows for mini marshmallows?
Yes, but you'll need 2 cups regular marshmallows (about 12 oz) instead of 3 cups mini marshmallows. Chop the regular marshmallows into small pieces first for even melting. Mini marshmallows create that signature "rivers" effect better, but regular marshmallows will still give you a delicious, caramelized top—just with slightly larger pockets of goo!
How do I make this casserole healthier?
Swap half the butter in the streusel for unsweetened applesauce or coconut oil to reduce fat. Use coconut sugar instead of brown sugar, and reduce the granulated sugar in the marshmallow topping by 1/4 cup. For extra fiber, add 1/2 cup oats to the streusel. The texture will be slightly different, but it'll still be delicious with 30% fewer calories!
Why does my streusel turn out greasy?
Greasy streusel usually means the butter wasn't cold enough when mixed or the flour wasn't properly incorporated. Next time, chill the butter for 30 minutes before cutting it into the flour, and mix just until combined—overmixing releases more butterfat. For extra insurance, sprinkle 1 tablespoon flour over the streusel before baking to absorb any excess moisture.