Description
This Sweet Potato Casserole with Marshmallows and Oat Streusel is a comforting, festive dish perfect for holiday gatherings. Creamy mashed sweet potatoes are topped with a layer of gooey mini marshmallows and a crunchy oat streusel made with brown sugar, butter, and spices. Baked until golden and bubbly, this casserole offers a perfect balance of sweet and spice with delightful textures, making it a beloved classic side dish.
Ingredients
Scale
Sweet Potatoes
- 3 medium sweet potatoes
- 1 teaspoon salt
- 2 tablespoons butter
- 1/4 cup milk
- 1 teaspoon pumpkin pie spice
Oat Streusel
- 4 tablespoons cold butter
- 1/4 cup brown sugar
- 1/4 cup flour
- 1/4 cup rolled/old fashioned oats
- 1/2 teaspoon baking powder
- 1/2 teaspoon pumpkin pie spice
- Pinch salt
Topping
- 3 cups mini marshmallows
Instructions
- Prepare the Sweet Potatoes: Peel and slice the sweet potatoes into 1-inch rounds. Place them in a large pot and sprinkle with 1 teaspoon of salt. Cover the potatoes with cold water.
- Cook the Potatoes: Place the pot on the stovetop over high heat. Cover and cook for 20-25 minutes or until the potatoes are tender and easily pierced with a fork.
- Drain and Steam Off Water: Carefully drain the water from the pot. Return the pot to medium heat uncovered for 1-2 minutes to evaporate any excess moisture from the potatoes.
- Mash the Potatoes: Remove the pot from heat. Add 2 tablespoons butter, 1/4 cup milk, and 1 teaspoon pumpkin pie spice. Gently mash the potatoes until smooth. Set aside or transfer to an airtight container if preparing ahead.
- Make the Streusel: Cut 4 tablespoons cold butter into marble-sized pieces. In a medium bowl, combine butter, 1/4 cup brown sugar, 1/4 cup flour, 1/4 cup oats, 1/2 teaspoon baking powder, 1/2 teaspoon pumpkin pie spice, and a pinch of salt.
- Form the Streusel Topping: Use two forks, a pastry cutter, or your fingers to cut the butter into the dry ingredients until coarse crumbs about the size of large peas form. Store in an airtight container if making ahead.
- Preheat Oven and Prepare Dish: Preheat oven to 350ºF. Grease a 2 ½ quart baking dish or one of a similar size.
- Assemble the Casserole: Spread the mashed sweet potatoes evenly in the baking dish. Layer the 3 cups mini marshmallows evenly over the potatoes. Sprinkle the oat streusel over the marshmallows.
- Bake: Place the casserole in the oven and bake for 18-20 minutes. Watch carefully to prevent the marshmallows from burning or overcooking.
- Rest Before Serving: Remove from the oven and let the casserole rest for at least 10 minutes. This allows it to set and prevents watery textures when serving.
- Make Ahead Tips: This casserole can be assembled up to 2 days in advance by storing the mashed potatoes, marshmallows, and streusel separately. When ready to bake, layer them in the baking dish and bake as directed. Bring the potatoes to room temperature for about 30 minutes before baking if stored in the fridge.
Notes
- Use cold butter for the streusel to ensure crumbly, crisp topping.
- Watch the marshmallows closely during baking as they can brown quickly.
- This dish stores well and can be reheated gently in the oven.
- Bring mashed sweet potatoes to room temperature before baking if preparing ahead for best results.
- The 2 ½ quart baking dish size is ideal for even cooking but a similar sized dish will work.
- For a nuttier streusel, you may add chopped pecans or walnuts if desired.
