Boston Market Copycat Sweet Potato Casserole with Marshmallows
A restaurant-style sweet potato casserole featuring creamy mashed sweet potatoes enriched with butter, brown sugar, and warm spices, topped with fluffy marshmallows and a crunchy oat streusel. This indulgent side dish balances sweet and savory flavors with contrasting textures, making it perfect for Thanksgiving, holiday gatherings, or any time you want a comforting casserole that feels special. The Boston Market-inspired recipe delivers the beloved combination of smooth sweet potato base and golden-brown topping that guests expect from this classic American dish.
Ingredients
- 4 pounds sweet potatoes, peeled and cut into 1 inch pieces
- 4 tablespoons unsalted butter
- ¾ cup light brown sugar, packed
- ½ cup heavy cream
- 1 teaspoon kosher salt
- 1 tablespoon pure vanilla extract
- 1 teaspoon ground cinnamon
- ¼ teaspoon ground nutmeg
- 2 cups mini marshmallows
- ½ cup all-purpose flouralmond flour1:1gluten-freegluten-free
may affect streusel texture
- 4 tablespoons unsalted butter
- 6 tablespoons light brown sugar, packed
- ¼ cup old fashioned rolled oats, not instant oats
- ¼ teaspoon ground cinnamon
Instructions
- 1
Preheat oven and grease casserole dish
- 2
Fill large pot with sweet potato pieces and water to cover by 2 inches
- 3
Bring to boil over high heat and cook until fork tender
- 4
Drain water and return potatoes to pot
- 5
Mash potatoes until mostly smooth using potato masher or electric mixer
- 6
Add butter, brown sugar, cream, salt, vanilla, cinnamon and nutmeg to potatoes and mix until combined
- 7
Spoon sweet potato mixture into casserole dish and smooth surface with wooden spoon
- 8
Sprinkle marshmallows over mashed sweet potatoes
- 9
Microwave butter in medium bowl until melted
- 10
Add flour, brown sugar, oats and cinnamon to melted butter and combine with fork
- 11
Sprinkle streusel mixture over casserole
- 12
Bake until streusel is crisp and marshmallows are golden brown
- 13
Serve while warm
Tips
Don't skip draining the sweet potatoes thoroughly - excess water will make the casserole watery and prevent proper texture
Make the streusel topping just before baking to keep the oats from getting soggy and ensure maximum crunch
Watch the marshmallows closely in the final minutes of baking as they can go from golden to burnt quickly
Good to Know
Refrigerate covered for up to 3 days, reheat in 350F oven until warmed through
Can assemble without topping up to 1 day ahead, add topping just before baking
Serve warm as a side dish, pairs well with roasted meats and traditional holiday fare
Common Mistakes
Don't overbake or marshmallows will burn and become bitter
Avoid instant oats in streusel as they become mushy during baking
Don't skip smoothing the sweet potato base or topping will sink unevenly
Substitutions
Gluten-Free Swaps
Nut-Free Alternatives
General Alternatives
FAQ
Can I make this without marshmallows?
Yes, simply omit the marshmallows and add extra streusel topping, or try chopped pecans for crunch. The casserole will still be delicious with just the oat topping.
What if I don't have heavy cream?
Substitute with evaporated milk, whole milk, or even buttermilk for tang. The texture will be slightly less rich but still creamy and flavorful.
How long will leftovers keep?
Store covered in refrigerator for up to 3 days. Reheat individual portions in microwave or whole dish in 350F oven until heated through.