To make ahead: Prepare the recipe through Step 4, then cover the casserole with plastic wrap and refrigerate for up to 3 days. Bake for 45 to 50 minutes, or until hot all the way through. Top with marshmallows and bake for a few more minutes until the marshmallows have melted.
- 8 sweet potatoes (about 4 pounds)
- 1/4 cup plus 1 tablespoon unsalted butter, softened at room temperature
- Finely grated zest of 1 orange
- 1/2 cup fresh-squeezed orange juice
- 1/2 teaspoon salt
- 1/8 teaspoon pepper
- 4 cups large marshmallows (about 12 ounces), cut in half with scissors
1 Roast the sweet potatoes: Preheat the oven to 425ºF. Line a baking sheet with parchment and spray it with vegetable oil spray.
Scrub clean and dry the sweet potatoes. Slice them in half lengthwise.
Place the potato halves, cut side down, on the baking sheet. Prick each in several places with a fork and bake for 40 to 45 minutes, or until soft. Remove and let rest until potatoes are cool enough to handle.
2 Lower the oven temperature to 375ºF. Butter or coat with cooking spray a 3-quart or 9-x13-inch baking dish.
3 Remove the sweet potato skins: As soon as the potatoes are cool enough to handle, pull off the skins and discard. Transfer the inner flesh to the bowl of a stand mixer bowl fitted with the paddle attachment, or a large bowl.
4 Mash the potatoes: Add 1/4 cup of the butter, orange zest, orange juice, salt and pepper. Mix on low speed in the stand mixer until the potatoes are creamy, but not necessarily perfectly smooth. Taste and add more salt and pepper, if you like. Transfer the potatoes to the buttered baking dish.
Alternatively, mash with a potato masher and beat until creamy with a wooden spoon, then transfer to the baking dish.
4 Bake the casserole: Dot the top of the casserole with the remaining 1 tablespoon of butter. Cover loosely with foil and bake for 30 to 35 minutes, or until hot.
5 Add the marshmallows: Place the marshmallows close together in a random pattern over the potatoes. Return the casserole to the oven and bake for 5 to 7 minutes, or until the marshmallows melt and brown.
6 Serve: Cool the casserole briefly and serve while hot. Leftovers can be refrigerated for up to 5 days.