- 2 lb sweet potatoes (2 or 3 large)
- 7 large egg yolks
- 3 tablespoons packed light brown sugar
- 1 teaspoon fresh lemon juice
- 1/2 teaspoon freshly grated nutmeg
- 1/2 teaspoon salt
- 3 cups whole milk
- 5 to 7 tablespoons turbinado sugar such as Sugar in the Raw
- Special equipment: a shallow 2 1/2-qt flameproof baking dish such as a 12-inch quiche dish (1 3/4 inches deep); a small blowtorch
- Put oven rack in middle position and preheat oven to 400°F.
- Pierce potatoes all over with a fork. Bake in a foil-lined shallow baking pan until tender, about 1 hour. Remove from oven and reduce oven temperature to 300°F.
- When sweet potatoes are cool enough to handle, peel them. Cut warm potatoes into 2-inch pieces and purée in a food processor until smooth.
- Whisk together yolks, brown sugar, lemon juice, nutmeg, and salt in a large bowl until sugar is dissolved. Whisk in sweet-potato purée until combined, then gently stir in milk until combined. Pour mixture into baking dish and bake until custard is just set, about 1 hour. Cool in dish on a rack 1 hour (custard will continue to set as it cools).
- Just before serving, gently sprinkle enough turbinado sugar over custard to cover evenly (top of custard may be very soft), then move blowtorch flame evenly back and forth just above sugar until sugar is caramelized, about 3 minutes. Let stand until topping is hardened, 3 to 5 minutes.