Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe

If you have a soft spot for warm, comforting dishes that bring a touch of sweetness and a bit of crunch, the Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe is an absolute must-try. This recipe combines fluffy mashed sweet potatoes infused with cozy pumpkin pie spice, a golden oat streusel topping with just the right amount of crunch, and a gooey layer of toasted mini marshmallows that make every bite heavenly. It’s a classic dish with a twist, perfect for holiday feasts or whenever you crave something both nostalgic and delightfully unique.

Ingredients You’ll Need

This Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe relies on straightforward, wholesome ingredients that work in harmony to deliver incredible flavor and texture. Each component has a role in balancing creaminess, sweetness, and crispness, making this dish truly irresistible.

• 4 tablespoons butter, cold: Adds a rich, creamy texture and helps bind the streusel topping perfectly.
• 1/4 cup brown sugar: Brings warm sweetness and a slight molasses flavor to the topping.
• 1/4 cup flour: Provides structure to the oat streusel so it crisps up nicely.
• 1/4 cup rolled/old fashioned oats: Adds a hearty, crunchy texture to the streusel topping.
• 1/2 teaspoon baking powder: Lightens the topping just a touch for balanced crispness.
• 1/2 teaspoon pumpkin pie spice: Infuses the dish with a warm, aromatic blend of cinnamon, nutmeg, and cloves.
• Pinch salt: Enhances all the flavors and balances the sweetness beautifully.
• 3 medium sweet potatoes: The star ingredient providing natural sweetness and creamy texture.
• 1 teaspoon salt: Used in boiling the potatoes to season them from within.
• 2 tablespoons butter: Incorporated into the mashed sweet potatoes for richness.
• 1/4 cup milk: Keeps the mashed potatoes smooth and luscious.
• 1 teaspoon pumpkin pie spice: Added to mashed potatoes for that extra layer of cozy flavor.
• 3 cups mini marshmallows: The crowning glory that melts into a sweet, gooey layer on top.

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

Step 1: Prepare and Cook the Sweet Potatoes

Begin by peeling your sweet potatoes and slicing them into 1-inch rounds, which helps them cook evenly and faster. Place the slices in a large pot, sprinkle in the 1 teaspoon of salt, and cover with cold water. Starting with cold water helps the potatoes cook through gently without being mushy.

Step 2: Boil Until Tender

Put the pot on high heat, cover, and bring the water to a gentle boil. Let the potatoes cook for 20 to 25 minutes, or until you can easily pierce them with a fork. This step is crucial for achieving the perfect creamy base for your casserole.

Step 3: Drain and Steam Off Excess Water

Drain the water carefully, then return the pot to medium heat uncovered for about 1 to 2 minutes. This removes any lingering moisture and ensures your mashed sweet potatoes won’t be watery, which is key to a thick, cozy casserole.

Step 4: Mash and Season

Remove the pot from heat and add butter, milk, and pumpkin pie spice. Gently mash the potatoes until smooth and creamy. This mixture is the luscious foundation of your casserole—rich with buttery flavor and just the right hint of spice.

Step 5: Make the Oat Streusel Topping

Cut the cold butter into small marble-sized pieces, then combine it with brown sugar, flour, oats, baking powder, pumpkin pie spice, and a pinch of salt in a medium bowl. Using two forks, a pastry cutter, or your fingers, mix the butter into the dry ingredients until you have crumbly clusters about the size of large peas. This streusel brings that satisfying crunch that contrasts beautifully with the marshmallows and sweet potatoes.

Step 6: Prepare for Baking

Preheat your oven to 350ºF and grease a 2 ½ quart baking dish, or something close in size. Spread the mashed sweet potatoes evenly into the dish, smoothing the top for a nice base layer.

Step 7: Add the Marshmallows and Streusel

Top the sweet potatoes with an even layer of mini marshmallows, then sprinkle the oat streusel generously over the marshmallows. It’s this layering that creates a delightful combination of gooey marshmallow softness and crunchy oat topping once baked.

Step 8: Bake to Perfection

Pop the casserole into your oven and bake for 18 to 20 minutes. Keep an eye on it so the marshmallows toast just right and don’t overcook. The end result should be bubbling with melted marshmallows and a crisp, golden streusel crown.

Step 9: Let It Rest Before Serving

Once out of the oven, allow the casserole to rest for at least 10 minutes. This resting time lets the layers set nicely, preventing your dish from becoming watery when you cut into it. Trust me, this step makes all the difference for a perfect slice!

Step 10: Prep Ahead Tips for This Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe

You can absolutely prepare this dish up to two days ahead. Keep the mashed sweet potatoes stored in the baking dish, the streusel topping in an airtight container in the fridge, and portion out the marshmallows separately for easy layering right before baking. Bring the sweet potatoes to room temperature before assembling and baking for best results.

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

Garnishes

For an extra touch of charm, sprinkle some toasted chopped pecans or walnuts over the streusel before baking. They add a lovely nutty crunch that complements the soft marshmallows flawlessly. A light dusting of cinnamon or a drizzle of maple syrup just before serving can also elevate the dish beautifully.

Side Dishes

This Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe pairs wonderfully with savory mains like roasted turkey, glazed ham, or even a simple grilled chicken. The sweet and spicy flavors provide a delicious contrast to hearty, protein-forward dishes, making it a perfect companion for holiday spreads or family dinners.

Creative Ways to Present

For a festive presentation, bake the casserole in small individual ramekins to serve personal portions. Alternatively, add a scattering of fresh cranberries around the edge of the serving dish or place a sprig of fresh rosemary on top to brighten the look. Either way, this dish will steal the spotlight when it arrives at the table.

Make Ahead and Storage

Storing Leftovers

Simply cover any leftover casserole tightly and refrigerate for up to 3 days. The flavors meld nicely overnight, but the marshmallows and streusel topping might soften slightly, which is easily fixed with a quick reheat.

Freezing

You can freeze the casserole by assembling it without the marshmallows and streusel toppings. Store it in an airtight container or foil-covered dish for up to 2 months. When ready to enjoy, thaw overnight in the fridge, then add the marshmallows and streusel before baking fresh as instructed.

Reheating

Reheat leftovers in a 350ºF oven covered with foil to prevent drying out, for about 15-20 minutes until warmed through. For that fresh-from-the-oven marshmallow gooeyness, add a few extra mini marshmallows on top and broil for 1-2 minutes at the end.

FAQs

Can I use canned sweet potatoes instead of fresh?

While fresh sweet potatoes make for the best texture and flavor, canned sweet potatoes can work in a pinch. Just be sure to drain them well and mash thoroughly before layering. The dish might be a little less fluffy but still delicious.

Is it possible to make this recipe vegan?

Absolutely! Substitute the butter with vegan margarine or coconut oil and use a plant-based milk like almond or oat milk. Choose vegan mini marshmallows to keep the dish totally plant-based while retaining that classic taste and texture.

What’s the best way to prevent the marshmallows from burning?

Keep a close eye during baking and consider tenting the dish with foil if the marshmallows start browning too quickly. You can also add the marshmallows partway through baking for a softer, less toasted finish.

Can the oat streusel topping be made crunchier?

Yes! To get an even crunchier topping, try adding chopped nuts or increasing the amount of oats slightly. Just be sure to keep the butter proportionate so everything binds well and breadcrumbs form properly.

How long can I prep this dish ahead of time?

You can prepare all the components separately and store them up to 2 days in advance. Assemble just before baking for the best texture and freshness.

Final Thoughts

There is something truly magical about the Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe—a dish that feels like a warm hug on a plate. It’s perfect for sharing with loved ones during special occasions or anytime you want to elevate your dinner table with a bit of sweetness and crunch. Give it a try, and I promise it will become a treasured favorite in your kitchen too!

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