Line a baking sheet with foil and place the potatoes on the foil to bake.
Bake until tender for about 1 hour. You want them to be extra soft.
Cut them open and scoop out the sweet potato and place in a bowl, leaving the skin behind.
Mash the sweet potatoes with butter, sugar, salt, vanilla, and heavy cream while they’re hot.
Mash until the texture is smooth or how you like it. You can also use an electric mixer or blender to get smooth potatoes.
Spread the mashed sweet potatoes into a casserole dish.
Top with regular or large marshmallows, OR spread the homemade marshmallow fluff over the mashed sweet potatoes.
If you're using marshmallows, bake the dish in a 350-degree oven for 5 mins or until the marshmallows are golden brown.
Using a kitchen torch, torch the marshmallow fluff until it’s toasty!
Notes
Marshmallows: For a classic topping, add an even layer of mini or large marshmallows after assembling the casserole. Bake at 350°F for 5–10 minutes until gooey and golden.
Make-Ahead Tip: If prepping ahead, leave the marshmallows off. Wrap and refrigerate the casserole for up to two days, then add marshmallows and bake when ready.
Marshmallow Fluff: Spread homemade fluff over the hot casserole, then use a kitchen torch to toast it until perfectly golden.
Leftovers: Store leftovers in an airtight container for up to two days. Reheat in the microwave or oven.
Freezing: Sweet potato casserole freezes well for up to two months. Thaw overnight in the fridge before reheating.