Sweet Potato Casserole With Marshmallows & Brown Sugar Streusel Recipe

I’m sharing my Sweet Potato Casserole With Streusel, where mashed sweet potatoes are topped with toasted marshmallows and a crisp streusel that hides a little twist.

I love the way sweet potatoes can be both savory and wildly indulgent in one bite. Sweet potatoes meet a cheeky crown of toasted marshmallows and somehow spark debate at every dinner table.

Some call it Sweet Potato Casserole With Streusel while others stick to the Sweet Potato Casserole With Marshmallows classic. I keep a small, sneaky trick that makes the topping sing, its the one thing guests always ask about but I tease it out so they keep guessing.

Every year someone claims the streusel wins, someone else defends the marshmallow camp, and that argument is exactly why I keep making it.

Ingredients

• Sweet potatoes are full of fiber and beta carotene, kinda sweet and creamy
• Butter adds richness and fat, boosts mouthfeel but ups calories and saturated fat
• Brown sugar gives caramel sweetness, mostly simple carbs, not much nutrition
• Eggs bind everything, add protein and moisture, they also add a bit richness
• Marshmallows melt into gooey topping, pure sugar, adds nostalgic sweet crunch
• Pecans give crunch, healthy fats, a little protein and lots of flavor
• Cinnamon adds warm spice, little calories, helps perception of sweetness
• Flour makes streusel structure, mostly carbs, pairs with butter and sugar

Ingredient Quantities

• 3 pounds sweet potatoes, peeled and cut into chunks (about 4 medium)
• 1/2 cup (1 stick) unsalted butter, softened
• 1/2 cup packed light brown sugar
• 2 large eggs, beaten
• 1/4 cup whole milk or heavy cream, plus a splash if needed
• 1 teaspoon vanilla extract
• 1/2 teaspoon ground cinnamon
• 1/4 teaspoon ground nutmeg
• 1/2 teaspoon kosher salt
• 4 cups mini marshmallows (about one 10 ounce bag)
• 1/2 cup all purpose flour
• 1/2 cup packed light brown sugar for streusel
• 1/2 cup chopped pecans (optional but makes it better)
• 1/3 cup cold unsalted butter, cut into small pieces (for streusel)
• 1/2 teaspoon ground cinnamon for streusel
• Pinch of salt for streusel

How to Make this

1. Preheat oven to 350°F (175°C). If you want extra sweet potato flavor you can roast whole sweet potatoes at 400°F for about 45 to 60 minutes instead of boiling, but the boil method is quicker.

2. Cook the sweet potatoes: with 3 pounds peeled and chunked sweet potatoes, boil in salted water until fork tender, about 15 to 20 minutes. Drain very well so they arent watery.

3. Mash and mix: put the hot potatoes in a bowl and mash until mostly smooth (use a ricer or hand mixer if you want ultra smooth). Stir in 1/2 cup (1 stick) softened unsalted butter, 1/2 cup packed light brown sugar, 2 large beaten eggs, 1/4 cup whole milk or heavy cream (plus a splash more if it seems thick), 1 teaspoon vanilla extract, 1/2 teaspoon ground cinnamon, 1/4 teaspoon ground nutmeg and 1/2 teaspoon kosher salt. Taste and adjust, but dont overbeat after adding the eggs or it’ll get gluey.

4. Transfer to a greased 9×13 inch baking dish and smooth the top with a spatula so its even.

5. Make the brown sugar streusel: in a bowl combine 1/2 cup all purpose flour, 1/2 cup packed light brown sugar, 1/2 cup chopped pecans (optional but makes it better), 1/2 teaspoon ground cinnamon and a pinch of salt. Cut in 1/3 cup cold unsalted butter, cut into small pieces, with a pastry cutter or your fingers until the mix is crumbly and clumps form.

6. Sprinkle the streusel evenly over the mashed sweet potato layer, pressing lightly so it adheres in spots.

7. Bake at 350°F for about 20 to 25 minutes, until the edges are bubbly and the streusel is set and starting to turn golden.

8. Remove from oven and evenly scatter 4 cups mini marshmallows (about one 10 ounce bag) over the top. Return to the oven and broil on high for 1 to 3 minutes until the marshmallows puff and get golden brown, watching like a hawk so they dont burn. If youre nervous about the broiler you can instead bake at 375°F for 8 to 10 minutes until marshmallows soften and brown lightly.

9. Let the casserole rest about 10 minutes to set before serving. Tip: you can assemble ahead and refrigerate (skip marshmallows), then bake 30 to 40 minutes covered/uncovered and add marshmallows and finish under the broiler. Dont walk away while broiling, it goes from perfect to burnt in seconds.

Equipment Needed

1. Oven with broiler function (for baking then toasting marshmallows)
2. 9×13 inch baking dish, greased
3. Large pot for boiling sweet potatoes (or rimmed baking sheet if you roast whole spuds)
4. Colander for draining
5. Potato masher, ricer, or hand mixer for mashing
6. Large mixing bowl (for the sweet potato mix)
7. Small bowl plus a pastry cutter or fork (for making streusel)
8. Rubber spatula or offset spatula to smooth the casserole top
9. Measuring cups and spoons, plus a knife and vegetable peeler for prepping potatoes

FAQ

Sweet Potato Casserole With Marshmallows & Brown Sugar Streusel Recipe Substitutions and Variations

• Sweet potatoes: canned sweet potato puree (use equal weight, stir in less milk if it seems watery) or roasted butternut squash (swap 1 to 1 by weight; it’ll be a bit nuttier in flavor).
• Unsalted butter (mash or streusel): use salted butter instead (same amount but cut the recipe salt by about 1/2 tsp) or cold coconut oil in the streusel (1:1, gives a slightly different texture and mild coconut note).
• Whole milk or heavy cream: evaporated milk works great (use same amount for a richer finish) or unsweetened almond milk plus 1 Tbsp melted butter for added fat if you need dairy free.
• Mini marshmallows: large marshmallows chopped up (use same volume) or marshmallow creme spread on top (won’t brown as easily unless you torch it) — you can also leave them off and add extra pecan streusel instead.

Pro Tips

1) Dry and texture matter. After draining the potatoes put them back in the hot pot for a minute or two and stir so extra steam evaporates, or they’ll water down the casserole. Use a ricer for super smooth, a hand mixer if you like slightly whipped, but once the eggs go in dont overbeat or it gets gluey.

2) Boost the flavor not the sugar. Roasting the whole sweet potatoes instead of boiling gives way more depth, and a little orange zest or a tablespoon of maple syrup or even a splash of bourbon lifts the taste without making it cloying. Toast the pecans in a dry pan with a pinch of salt first, they taste way better that way.

3) Make the streusel count. Keep the butter very cold and cut it in until you have noticeable clumps, that gives you the crunchy bits you want. If time allows chill the assembled dish for 10 to 15 minutes before baking so the streusel stays distinct instead of sinking in.

4) Finish smart with the marshmallows. Broil fast and watch it the whole time or use a kitchen torch for spot control, because it goes from perfect to burnt in seconds. If you’re doing this ahead, assemble without marshmallows and refrigerate, then bake until hot and add marshmallows at the end so theyre fresh and pillowy.