The classic sweet potato casserole with a crunchy brown sugar pecan topping AND melty marshmallows is a must have for the holidays. Plus directions on how to make this sweet potato casserole with just marshmallows or just pecans.
Preheat oven to 400 degrees F. Wash and deeply pierce each sweet potato several times with a fork and transfer to a foil-lined large cookie sheet. Bake 1 hour, or until very tender when pierced with a fork. Once fork tender, remove from the oven, allow to slightly cool, and then cut potatoes in half and pull off the skins (they should peel right off!)
If the skins don't come off easily, scoop out the flesh from the halved potatoes. Place into a large mixing bowl and mash the potatoes with a potato masher. Add in brown sugar, white sugar, butter, vanilla, evaporated milk, cinnamon, and salt. Blend, using electric hand mixers, on low speed until smooth. Add in eggs and beat until blended and smooth. Reduce oven temperature to 350 degrees F.
Smooth the sweet potato mixture into a 9 x 13 pan. In a separate bowl, combine pecan topping: the melted butter, chopped pecans, brown sugar, flour, and salt. Stir until ingredients are well incorporated. Either top the entire casserole with this mixture or top in rows. If you opt to do rows (as pictured) you'll have about 1/2 cup extra of the topping; if you top the entire casserole, you'll use all of the topping. Bake in 350 degree oven for 30 minutes (tent with foil if streusel is browning too quickly).
Remove casserole and add marshmallows (to desired preference) over the casserole -- either on top of the pecan topping or in between rows. If in between rows, you'll use about 1 and 1/2 cups. If you top the whole casserole, about 3 cups. Return to the oven and bake for 4-8 minutes or until marshmallows are melty and lightly golden (watch carefully!) Remove from oven and serve warm.
MAKE IN ADVANCE: You can make this casserole in advance! Just follow these tips: store the pecan topping and marshmallows separately. Cover the sweet potato casserole tightly and place in the fridge. When ready to bake, add pecan topping and place in the oven while it's preheating and then bake for 25-30 minutes once preheated. Add marshmallows according to recipe instructions.