Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe

If you’re looking for that unforgettable blend of comforting sweetness, a crunchy topping, and creamy mashed potatoes, then this Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe is exactly what you need on your table. It’s an absolute crowd-pleaser featuring velvety mashed sweet potatoes spiced just right, topped with toasty marshmallows and a crisp oat streusel that adds a delightful texture contrast. This dish strikes the perfect balance between nostalgic flavors and a rustic twist, making it a must-make for any holiday feast or cozy family dinner.

Ingredients You’ll Need

Don’t let the list intimidate you—this recipe relies on simple fundamentals that come together to build layers of warmth and flavor. Every ingredient plays a critical role, whether it’s the sweet and tender potatoes, the aromatic spices, or the buttery streusel that crowns the dish with a crunch.

• 4 tablespoons butter, cold: Essential for richness in the streusel and the mashed potatoes.
• 1/4 cup brown sugar: Adds a deep caramel sweetness to the oat topping.
• 1/4 cup flour: Helps bind the streusel crumbs together nicely.
• 1/4 cup rolled/old fashioned oats: Gives the topping that hearty, crunchy texture.
• 1/2 teaspoon baking powder: Lightens the streusel for a perfect crumb.
• 1/2 teaspoon pumpkin pie spice: Brings cozy autumnal warmth throughout the dish.
• Pinch salt: Balances sweetness and enhances flavors.
• 3 medium sweet potatoes: The star of the show, providing creamy, naturally sweet base.
• 1 teaspoon salt: Used for seasoning the potatoes during boiling to enhance their natural flavor.
• 2 tablespoons butter: Added to mashed potatoes for a luscious texture.
• 1/4 cup milk: Creates a smooth, creamy mash.
• 3 cups mini marshmallows: The fun, fluffy topping that melts into golden perfection.

How to Make Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe

Step 1: Prep and Boil the Sweet Potatoes

Start by peeling and slicing your sweet potatoes into 1-inch rounds—they’ll cook faster and mash beautifully. Place them in a large pot with 1 teaspoon of salt and cover with cold water. This salt addition seasons the potatoes as they boil, enhancing their natural sweetness.

Step 2: Cook Until Tender

Bring the pot to a boil on high heat, then cover and simmer for about 20 to 25 minutes. You’ll know the sweet potatoes are done when a fork pierces through easily. This step ensures a nice creamy texture once mashed.

Step 3: Drain and Dry Potatoes

Drain the potatoes carefully, then return the pot to medium heat uncovered for 1 to 2 minutes to evaporate any excess moisture. This small move prevents watery mash and helps create the perfect consistency.

Step 4: Mash with Butter, Milk, and Spice

Off the heat, add in the butter, milk, and pumpkin pie spice. Gently mash the sweet potatoes until smooth but still a bit textured. The spice adds a lovely hint of warmth that transforms the mash into a flavor-packed base layer.

Step 5: Make the Oat Streusel

Cut the cold butter into marble-sized pieces. Combine it with brown sugar, flour, oats, baking powder, pumpkin pie spice, and a pinch of salt in a medium bowl. Use forks, a pastry cutter, or fingers to cut the butter into the mixture until you form large pea-sized crumbs. This streusel adds the irresistible crunch and sweet nutty finish.

Step 6: Prepare the Baking Dish

Grease a 2 ½ quart baking dish generously. Spread the mashed sweet potatoes evenly in the dish, smoothing the top for an even layer. This is your comforting, creamy base that’s begging for its delicious toppings.

Step 7: Add Marshmallows and Streusel

Scatter the mini marshmallows evenly over the sweet potato layer. Then gently sprinkle the oat streusel on top. The marshmallows will melt down, melding with the soft sweet potatoes, while the streusel crisps up beautifully in the oven.

Step 8: Bake to Golden Perfection

Bake your creation at 350ºF for 18-20 minutes. Keep an eye on the marshmallows; you want them toasted and bubbly but not burnt. The smell filling your kitchen at this stage will be simply irresistible.

Step 9: Let it Rest Before Serving

Once out of the oven, give the casserole at least 10 minutes to rest. This step allows the layers to set, preventing the buttery topping and sticky marshmallows from being too runny when served.

How to Serve Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe

Garnishes

For an extra touch, sprinkle a few chopped toasted pecans or walnuts on top just before serving. Freshly chopped parsley can also add a subtle color contrast and a hint of herbaceous freshness against the sweetness.

Side Dishes

This casserole pairs beautifully with savory mains like roasted turkey, glazed ham, or herb-crusted chicken. Light, crisp salads can balance out the richness, making for a well-rounded meal.

Creative Ways to Present

Try serving individual portions in mini ramekins for a charming, personalized touch at your next dinner party. You can also layer the casserole in a trifle-style glass dish to show off the beautiful layers and textures inside.

Make Ahead and Storage

Storing Leftovers

Wrap leftovers tightly and refrigerate for up to three days. The flavors meld nicely overnight, transforming each serving into an even more delightful bite the next day.

Freezing

This Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe freezes well if you store each component separately before baking. Freeze mashed sweet potatoes in an airtight container, and keep your marshmallows and streusel in separate bags. Assemble and bake fresh when ready.

Reheating

Reheat leftovers in a 350ºF oven until warmed through, about 15-20 minutes. To avoid drying out, cover loosely with foil and remove it during the last 5 minutes to crisp the top again.

FAQs

Can I use canned sweet potatoes for this recipe?

While fresh sweet potatoes are preferred for their texture and flavor, you can use canned sweet potatoes in a pinch. Just make sure to drain them well and adjust mashing textures accordingly.

Is it possible to make this casserole vegan?

Yes, by substituting the butter with vegan margarine, using plant-based milk, and selecting vegan marshmallows, you can make a delicious vegan version that maintains all the original charm.

How long can I make the casserole ahead of time?

You can prepare all three layers separately up to two days in advance. Store the mashed potatoes in the baking dish, keep the streusel chilled in a container, and measure out marshmallows to layer fresh before baking.

What can I substitute for pumpkin pie spice?

If you don’t have pumpkin pie spice, mix equal parts cinnamon, nutmeg, ginger, and a pinch of cloves for a homemade version that captures the warm, spiced flavor.

Why should I let the casserole rest after baking?

Allowing the casserole to rest lets the layers firm up, ensuring easy serving and preventing the buttery topping and melted marshmallows from running. It also enhances flavor melding for every bite.

Final Thoughts

This Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe is truly one of those dishes that brings smiles and nostalgia to any occasion. Its irresistible combination of creamy, sweet, and crunchy elements makes every spoonful a comforting delight. Give it a try soon—you’ll be so glad you did, and your family and friends will be asking for seconds in no time!

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