This Sweet Potato Casserole with Marshmallows and Brown Sugar Streusel is a show-stopping holiday side dish. Inspired by the famous Ruth’s Chris version, this recipe balances light, fluffy sweet potato soufflé with gooey mini marshmallows and a buttery brown sugar streusel for a topping that’s simultaneously crunchy and melt-in-your-mouth. It’s easy to prepare, feeds a crowd, and is a favorite with kids.
We made this again for Thanksgiving and it was hands down the best side on the table. It’s excellent for Christmas, Easter, or any special family meal where you want a comforting, slightly sweet side that borders on dessert.
Sweet Potato Soufflé with Marshmallows
A few years ago my then-toddler helped me make this casserole and proudly announced she’d made “the best dinner ever.” It’s not a full meal on its own, but it does have that magic that gets kids (and grownups) excited about sweet potatoes. Unlike the overly syrupy, mushy casserole versions many of us remember, this recipe produces a light, airy soufflé-like interior with rich flavor and just the right sweetness.
Ingredients
To make this sweet potato casserole with marshmallows and brown sugar streusel you’ll need:
- Sweet potatoes – the base: naturally sweet and creamy
- Unsalted butter – for richness and a smooth texture
- Salt – to enhance and balance the sweetness
- Granulated sugar – to sweeten the mashed potatoes
- Brown sugar – for the streusel and caramel notes
- Cinnamon – warm spice that complements the potatoes (pumpkin pie spice works too)
- Vanilla extract – a subtle flavor boost
- Whole milk or heavy cream – to make the mash silky
- Egg – essential for the soufflé-like texture
- Mini marshmallows – classic melt-in-the-mouth topping
- All-purpose flour, cold butter, panko and graham cracker crumbs – for the brown sugar streusel topping
How to Make Sweet Potato Casserole
This dish takes a few more steps than dumping canned yams into a pan, but it’s straightforward and worth the effort. Overview:
- Bake: Pierce whole sweet potatoes and roast until fork-tender (about 45–60 minutes depending on size).
- Peel and mash: Let the potatoes cool slightly, remove the skins, and mash until smooth in a large bowl.
- Mix: Add the egg, melted butter, salt, granulated and brown sugars, cinnamon, milk or cream, and vanilla. Beat until smooth and airy — a handheld or stand mixer helps create the soufflé texture.
- Bake base: Spread the mixture in an 8×9 (or 8×8/9×9) baking dish and bake at 350°F for about 30 minutes until set and lightly golden.
- Top and finish: Cover the baked sweet potato layer with mini marshmallows, then sprinkle the brown sugar streusel over the marshmallows. Return to the oven for 20 minutes or until the topping is bubbly and golden.
- Rest: Let rest 5–10 minutes before serving so the casserole sets slightly and is easier to portion.
Tips for Success
- For extra-smooth potatoes: use a potato ricer instead of a masher.
- Roast until very soft: sweet potatoes are done when they begin to release juice and are easily pierced with a fork.
- Don’t skip the egg: it gives the mash its soufflé-like lift and structure.
- Marshmallow swap: if you don’t have mini marshmallows, roughly chop regular marshmallows.
Variations: Canned Sweet Potatoes and Nuts
You can use canned sweet potatoes in a pinch — be sure to drain them very well before mashing. If you like nuts, sprinkle chopped pecans or walnuts over the streusel when you add the marshmallows for extra crunch and flavor.
Make-Ahead Instructions
- Bake and mash the sweet potatoes ahead of time and store in an airtight container in the refrigerator.
- Prepare the streusel topping in advance and freeze in a zipper bag for up to a month.
- Assemble the soufflé in the dish the day before and refrigerate (leave the marshmallows and streusel off until baking day).
- Bake on the day you plan to serve it so the marshmallows stay fresh and gooey.
You can also freeze the casserole (without marshmallows and streusel). Thaw before baking, add the toppings, and finish in the oven.
Storing and Reheating
Store leftovers in an airtight container in the refrigerator for up to 5 days.
To reheat, warm the whole casserole in a 300°F oven until heated through, or reheat individual portions in the microwave for a quick option. Reheating gently helps keep the topping pleasant — not burnt or overly dried.
This is the best sweet potato casserole with marshmallows in my book: easy to make, rich in flavor, and topped with a contrast of gooey marshmallows and crunchy streusel that makes it an unforgettable holiday side that can even double as a dessert.
More Thanksgiving Side Dishes:
- Lemon Mandarin Orange Jello Salad
- Southern Grape Salad with Pecans
- Instant Pot Southern Macaroni and Cheese
- Southern English Pea Salad
- Southern Macaroni and Cheese
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