Sweet Potato Casserole Recipe With Streusel and Marshmallows: Crispy Streusel Crown Over Gooey Marshmallow Rivers

This sweet potato casserole recipe delivers the perfect balance of textures—crispy streusel crown over velvety spiced sweet potatoes and rivers of golden, gooey marshmallows. 🔥 The secret lies in layering: tender sweet potatoes form the base, while a buttery streusel topping transforms into a caramelized crust, and marshmallows toast to perfection without burning.

I've perfected this technique over years of holiday gatherings, ensuring every bite delivers that satisfying contrast of textures and flavors.

The foundation starts with properly cooked sweet potatoes—whether mashed or sliced, they must be perfectly tender yet hold their shape when baked. The streusel topping, made with flour, butter, and brown sugar, gets pressed firmly into the casserole before adding marshmallows, creating that iconic crispy crown.

Baking at the right temperature (350°F) ensures the marshmallows caramelize beautifully while the streusel stays golden and crunchy.

What you'll end up with is a showstopping side dish that's foolproof and restaurant-quality at home. The sweet potatoes stay moist and flavorful, the streusel transforms into a buttery, caramelized blanket, and the marshmallows create golden rivers that ooze with every bite.

This is the kind of casserole that disappears quickly at holiday tables and becomes an instant family favorite.

Perfect for Thanksgiving, Christmas dinners, or any gathering where you want to impress with minimal effort. The best part? It's a crowd-pleaser that even picky eaters can't resist. Let's get baking!

Ingredients for sweet potato casserole recipe with streusel and marshmallows

The perfect trifecta: velvety sweet potatoes, buttery streusel crown, and marshmallow rivers that ooze with every bite.

The sweet potatoes are the heart of this dish—use orange-fleshed varieties like Beauregard for the best texture. Costco or Trader Joe's always have them pre-peeled and ready to cook, saving you time. For the streusel, cold butter is non-negotiable—it creates those perfect flaky layers. I always grab Land O'Lakes unsalted butter for consistency, but any good brand works. The marshmallows? Kraft or Jet-Puffed mini marshmallows are my go-to—they toast perfectly without burning. Pro tip: buy them in bulk during holiday season when they're on sale.

No brown sugar? White sugar plus a pinch of molasses works in a pinch, though the streusel won't have that rich caramel flavor. Short on flour? Almond flour at 1:1 ratio adds a nice nutty twist. The evaporated milk can be swapped for whole milk plus 1 tbsp cornstarch if needed. For the sweet potatoes, if you prefer them sliced instead of mashed, roast them at 400°F for 25 minutes first to soften before layering. And if you're watching sugar, reduce the marshmallows by half and add 1 tbsp maple syrup to the sweet potato mix—trust me, it still tastes amazing.

This casserole tastes even better the next day—make it ahead and bake fresh when guests arrive. Store leftovers in an airtight container for up to 4 days, though I've never had any last that long. For freezing, assemble completely (including marshmallows) and bake until just golden, then cool and freeze for up to 3 months. To reheat, cover with foil and warm at 350°F for 20 minutes. The streusel will soften slightly but still hold its magic—just broil for 2 minutes at the end if you want extra crispiness.

Step-by-step instructions for sweet potato casserole with streusel and marshmallows

Here's how to create that perfect balance of crispy streusel, creamy sweet potatoes, and golden marshmallow rivers.

Peel the 4 whole large sweet potatoes and cut them into 1-inch chunks. Place them in a large pot and cover with water by about 2 inches. Add the 0.5 tsp salt and bring to a boil over medium-high heat. Reduce to a simmer and cook for 12-15 minutes until fork-tender.

Drain the sweet potatoes thoroughly, then return them to the pot. Add the 0.5 cup granulated sugar, 0.5 cup evaporated milk, 1 tsp vanilla extract, and 0.25 cup heavy cream (if using). Mash until smooth but still slightly textured—you want a thick, spreadable consistency. Let it cool completely before assembling, or the marshmallows will melt prematurely.

In a large bowl, combine the 1.5 cups all-purpose flour, 1 cup light brown sugar, 1 tbsp ground cinnamon, and 0.5 tsp ground nutmeg. Whisk until evenly distributed. Add the 1 cup cold cubed unsalted butter and use your fingers or a pastry cutter to work it into the mixture until it resembles coarse crumbs with pea-sized butter pieces remaining.

Add the 1 whole large egg and mix gently with a fork until just combined. The streusel should hold together when pressed, but don't overmix or it'll become dense. Press half of the streusel mixture into a 9x13-inch baking dish, spreading it evenly to create a firm base. This layer will crisp beautifully under the marshmallows.

Spread the cooled sweet potato mixture evenly over the streusel base, pressing down gently to create a smooth layer. This ensures even contact with the streusel below, which helps create that perfect crispy bottom layer. Sprinkle the remaining streusel evenly over the top of the sweet potatoes, pressing down lightly to help it adhere.

Arrange the 4 cups mini marshmallows in an even layer over the streusel. I like to pack them closely together so they form a continuous blanket—this creates those beautiful golden rivers when they melt. If any gaps appear, gently press additional marshmallows into place. The marshmallows should cover the entire surface without peeking over the edges.

Preheat your oven to 350°F and bake the casserole for 35-40 minutes until the edges of the streusel are deep golden brown and the marshmallows are puffed and beginning to turn golden. Watch closely during the last 10 minutes—the marshmallows go from perfect to burnt quickly.

For that restaurant-quality finish, broil for 1-2 minutes at the end, keeping a close eye to prevent burning. The marshmallows should be golden and slightly caramelized on top while still soft inside. Let the casserole rest for 5 minutes before serving—this allows the marshmallows to set slightly and makes cutting easier.

Essential equipment for this dish

Baking Dish Essentials

The right baking dish makes all the difference for that perfect streusel crown. I always use a 9x13-inch dark metal baking pan—it absorbs and radiates heat better than glass, creating even browning. Wilton Professional Baking Pans are my go-to because they're durable and non-stick.

If you don't have one, a ceramic dish works too, but increase baking time by 5-7 minutes to compensate for slower heat transfer. Avoid glass if you're short on time—they require lower temps and longer baking. 🔥

Mixing Tools Matter

For the streusel topping, I reach for a wooden spoon or pastry cutter to incorporate the cold butter—this prevents overmixing and creates those perfect crumbly pockets. A hand mixer works in a pinch, but I find it can overwork the dough.

For the sweet potato mixture, a potato masher gives the best texture, but a fork works if you're in a hurry. I keep a small offset spatula on hand to spread the sweet potato layer evenly before adding marshmallows. 🥄

Essential Measuring Tools

Precision is key for this recipe, so I always use a digital kitchen scale for the streusel ingredients—especially the butter and sugar. For dry ingredients, a stainless steel measuring cups (like OXO Good Grips) gives the most accurate results.

The mini marshmallows should be measured by volume in a dry measuring cup, packed lightly but not pressed down. A fine-mesh sieve comes in handy for sifting the flour and spices into the streusel mixture. 📏

Oven Thermometer

Your oven's temperature display can be off by 25°F or more, which is critical for this recipe. I use a Thermoworks ThermoPop oven thermometer to verify my oven's accuracy before baking. Place it in the center rack while preheating—if it reads 350°F, you're good to go.

If it's lower, increase your oven temperature by 25°F to ensure proper browning. This small investment prevents undercooked streusel or burnt marshmallows. ⚡

Broiling Tools

The final broil step requires careful attention, so I keep a heat-resistant silicone spatula nearby to protect my hands. A wire cooling rack helps create airflow if you need to broil multiple batches. For extra safety, I use oven mitts when handling the hot baking dish.

Pro tip: Place the dish on the middle rack when broiling to avoid direct flame exposure. A timer is essential—set it for 1 minute, then check immediately to prevent burning. 🕒

Storage Containers

For leftovers, I transfer the casserole to a glass Pyrex storage container with a tight-fitting lid. The glass keeps the dish cold longer than plastic, and the lid prevents the streusel from drying out. If freezing, I use quart-sized freezer bags with the air squeezed out to prevent freezer burn.

Label everything with the date—this casserole tastes best within 4 days when refrigerated or 3 months when frozen. ✨

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