Description
This Sweet Potato Casserole with Marshmallows and Oat Streusel is a comforting and festive side dish perfect for holidays or anytime you crave a sweet and crunchy treat. It features creamy mashed sweet potatoes seasoned with warm pumpkin pie spice, topped with gooey mini marshmallows and a crunchy oat streusel made of butter, brown sugar, and oats. Easy to prepare ahead, this casserole bakes to golden perfection, balancing sweet, creamy, and crunchy textures in every bite.
Ingredients
Scale
Sweet Potatoes
- 3 medium sweet potatoes
- 1 teaspoon salt
- 2 tablespoons butter
- 1/4 cup milk
- 1 teaspoon pumpkin pie spice
Streusel Topping
- 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 of salt
Other
- 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 with 1 teaspoon of salt and cover with cold water to start cooking evenly.
- Boil the Potatoes: Bring the pot to a boil over high heat. Cover and cook for 20-25 minutes until the sweet potatoes are tender and easily pierced with a fork.
- Drain and Steam Dry: Carefully drain the water from the pot. Return the pot to medium heat uncovered for 1-2 minutes to allow any excess water on the potatoes to evaporate, ensuring they won’t be watery when mashed.
- Mash the Sweet Potatoes: Remove from heat and add 2 tablespoons of butter, 1/4 cup milk, and 1 teaspoon pumpkin pie spice to the potatoes. Gently mash to a smooth consistency and set aside or refrigerate until ready to assemble the casserole.
- Make the Streusel Topping: Cut 4 tablespoons of cold butter into marble-sized pieces and add to a medium bowl with 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.
- Combine Streusel Ingredients: Using two forks, a pastry cutter, or your fingers, mix the cold butter into the dry ingredients until coarse crumbs form about the size of large peas.
- Preheat Oven: Preheat your oven to 350ºF (177ºC) and grease a 2 ½ quart baking dish or a similar size dish for the casserole.
- Assemble Sweet Potato Layer: Spread the mashed sweet potatoes evenly and smoothly in the prepared baking dish.
- Add Marshmallows: Evenly layer 3 cups of mini marshmallows over the sweet potato layer.
- Top with Streusel: Sprinkle the oat streusel mixture gently over the marshmallows.
- Bake the Casserole: Place the casserole in the preheated oven and bake for 18-20 minutes. Watch closely to prevent the marshmallows from over-browning.
- Rest Before Serving: Remove from oven and let the casserole sit for at least 10 minutes. This rest period allows the dish to firm up and prevents watery texture when cutting.
- Make-Ahead Tips: The sweet potato mixture, marshmallows, and streusel topping can be prepared up to 2 days ahead and stored separately. Assemble and bake as directed when ready to serve, allowing the sweet potatoes to come to room temperature if refrigerated.
Notes
- The casserole works best with a 2 ½ quart baking dish but any close size will suffice.
- Keep an eye on the marshmallows during baking to avoid burning or overcooking.
- You can prepare each layer ahead of time and store separately for up to 2 days in the fridge.
- Letting the dish rest after baking helps solidify the layers to prevent watery texture.
- If desired, you can substitute regular rolled oats with gluten-free oats to accommodate gluten sensitivities.
