Sweet Potato Casserole Recipe (Marshmallow or Pecan Streusel)

Sweet potato casserole is a smooth, mashed sweet potato base baked until set, then topped with either mini marshmallows or a pecan streusel and browned in the oven, a distinctly different dish from candied yams, which keeps the sweet potato in whole sliced pieces.

I used to think candied yams and sweet potato casserole were just two names for the same Thanksgiving dish. They’re not. One is soft, glazed chunks. This one is a smooth, almost dessert-like mash with a topping that gets its own moment under the broiler.

Both toppings have real, loyal camps. This covers both, plus the one step that decides whether your base turns out watery or holds together properly.

Key Takeaways

• Roasting the sweet potatoes whole gives a deeper, more caramelized flavor and a drier base than boiling, which matters since boiled sweet potatoes absorb water and can make the casserole loose
• Eggs are what give the base its slight lift, not just flavor, so don’t skip or skimp on them
• Marshmallows go on in the last 10 to 15 minutes of baking, or under the broiler for just 30 to 90 seconds, since they burn fast
• Pecan streusel needs cold butter to stay clumpy and crisp instead of melting into the base before it bakes
• The mashed base can be made 1 to 2 days ahead, but add the topping fresh, right before baking

Roast, Don’t Boil, If You Want the Best Base

Boiling is faster, but sweet potatoes absorb water as they cook, and that extra moisture is the most common reason a casserole ends up loose or soupy instead of holding its shape when sliced.

Roasting whole sweet potatoes, skin on, pierced a few times with a fork, concentrates their natural sugar through caramelization and keeps the flesh drier going into the mash. It takes close to an hour instead of 30 minutes, but it’s the difference between a base that holds together and one that needs a cornstarch rescue halfway through baking.

Ingredients

Sweet potatoes, 4 to 4.5 lbs (5 to 6 medium): Roasted whole, then peeled and mashed.

Unsalted butter, 1/2 cup (1 stick), melted

Sugar, 3/4 to 1 cup: White sugar keeps the mash cleaner-tasting, letting the vanilla and topping carry more of the sweetness.

Eggs, 2 large: This is what gives the base its slight soufflé-like lift. Don’t skip these.

Vanilla extract, 1 teaspoon

Milk, cream, or evaporated milk, 1/4 to 1/3 cup: Evaporated milk is the more traditional Southern choice, since it was a reliable pantry staple in kitchens without steady fresh dairy.

Salt, 1/4 teaspoon

For the marshmallow topping: 2 to 3 cups mini marshmallows.

For the pecan streusel topping: 1 cup chopped pecans, 1/2 cup brown sugar, 1/3 cup flour, 4 tablespoons cold butter, cut into small pieces.

Equipment

A potato ricer gives the smoothest possible mash with the least effort, since it processes the flesh gently without overworking it. The OXO stainless steel potato ricer is what I reach for. A potato masher works fine too if a perfectly smooth texture isn’t the goal.

Go easy with a stand or hand mixer if you use one. Sweet potatoes release starch differently than white potatoes, and overmixing can turn the base slightly gummy instead of light.

A glass or ceramic baking dish heats more evenly than metal, which matters most under a marshmallow topping, since metal can create hot spots that scorch the edges before the center browns.

How to Make Sweet Potato Casserole

Step 1: Roast and mash the sweet potatoes

Preheat the oven to 400 degrees. Pierce the sweet potatoes a few times with a fork and roast on a foil-lined sheet pan for about an hour, until completely tender. Let cool slightly, then peel and mash or rice the flesh.

Step 2: Mix the base

Combine the mashed sweet potato with the melted butter, sugar, eggs, vanilla, milk, and salt. Mix just until smooth, since overmixing with a machine can make the texture gummy.

Step 3: Bake

Reduce the oven to 350 degrees. Spread the base in a buttered 9×13 dish and bake, uncovered, for 35 to 40 minutes.

Step 4: Add the topping

For marshmallows, scatter them over the top for the final 10 to 15 minutes of baking, or bake the base fully first and run it under the broiler for just 30 to 90 seconds to brown the marshmallows. Watch it the entire time under the broiler, since it goes from golden to burnt in seconds.

For the pecan streusel, combine the pecans, brown sugar, flour, and cold butter until it’s clumpy, not a paste, and scatter it over the base before baking so it has the full 35 to 40 minutes to crisp up.

The Marshmallow Question, and Where It Really Came From

Marshmallows on sweet potatoes trace back to a real, well-documented piece of food history. In 1917, the Angelus Marshmallow company hired food writer Janet McKenzie Hill to develop a promotional recipe booklet meant to get home cooks using marshmallows in everyday dishes, and that booklet is credited with the first known pairing of marshmallows with sweet potatoes.

Worth being precise about: sweetened sweet potato dishes already existed well before 1917. What Angelus popularized was the marshmallow pairing specifically, not the idea of a sweetened sweet potato dish itself. The pecan streusel version has its own long, separately documented history in Southern community cookbooks, so neither topping is more “authentic” than the other, they’re just two different traditions.

Storage and Make-Ahead

The mashed base can be made 1 to 2 days ahead. Spread it in the baking dish, cover, and refrigerate, but add the topping fresh right before baking rather than during the make-ahead window, so a streusel stays crisp and marshmallows stay fresh.

Refrigerate leftovers up to 4 days. Only the base freezes well, for up to 3 months, wrapped tightly, without the topping already on. Add fresh topping after thawing, since freezing an already-topped casserole ruins the topping’s texture.

Reheat in a 325 to 350 degree oven for 10 to 25 minutes, depending on whether you’re reheating a full dish or a portion.

FAQ