Sweet Potato Casserole with Marshmallow
YIELDS: 8 serving(s)PREP TIME: 20 minsTOTAL TIME: 1 hr 50 mins
4 tbsp. (1/2 stick) unsalted butter, melted, plus more for baking dish
1/4 tsp. freshly grated nutmeg
3 large eggs plus 4 large egg whites
1 1/2 tsp. pure vanilla extract, divided
Kosher salt and freshly ground black pepper
Step 1 Preheat oven to 375°F. Butter a 3-quart broiler-safe baking dish. Roast sweet potatoes on a baking sheet until tender, 60 to 70 minutes. Cut a slit in the top to release steam and let cool for 15 minutes.
Step 2 Scoop out sweet potato flesh (discard skins). Transfer to a food processor and process until completely smooth, 30 seconds. Add butter, brown sugar, nutmeg, cayenne pepper, whole eggs, and 1 teaspoon vanilla. Pulse until fully incorporated, 3 to 4 times. Season with salt and black pepper; transfer to the prepared dish.
Step 3 Bake until sweet potatoes are set, 20 to 25 minutes. Let stand for at least 10 minutes.
Step 4 Whisk together egg whites, granulated sugar, and cream of tartar in a bowl. Set the bowl over (but not in) a saucepan of simmering water and cook, whisking constantly, until sugar is dissolved and whites are very warm to the touch, 3 to 4 minutes; remove from heat. Beat with an electric mixer on low speed, gradually increasing speed to high, until glossy and soft peaks form, 4 to 6 minutes. Beat in the remaining 1/2 teaspoon vanilla.
Step 5 Heat the broiler with the rack in the middle position. Spoon meringue over cooled sweet potatoes. Broil until meringue is browned, 30 seconds to 1 minute.