1/2 cup hazelnuts
2 pounds whole jewel or garnet sweet potatoes, scrubbed
1/2 cup heavy cream
4 ounces (1 stick) unsalted butter, cut into small chunks
2 tablespoons brown sugar
1/4 teaspoon ground cinnamon
Pinch of ground nutmeg
Pinch of ground ginger
Kosher salt and freshly ground white pepper
1 teaspoon chopped fresh thyme or marjoram leaves (optional)
1 tablespoon minced flat-leaf parsley or chives
Preheat oven to 350 degrees. Spread the hazelnuts on a baking sheet and bake until golden brown, 10 to 12 minutes. Immediately empty them into a folded kitchen towel; fold the towel over them and rub the hazelnuts inside to remove their skins. Pick out the nuts and set aside to cool. Discard the skins. When the nuts have cooled, coarsely chop with a sharp knife or in a food processor fitted with the metal blade. Set aside.
Raise the oven temperature to 400 degrees F. Cover a baking sheet with foil. Pierce the sweet potatoes in a few places with the tip of a sharp knife and place on the baking sheet. Bake until very soft when pierced with a thin skewer or knife tip, 45 minutes to one hour. Remove from the heat and allow to cool until you can handle them.
Steady each cooked sweet potato with a folded kitchen towel and cut in half lengthwise, taking care to keep your hands clear of steam. Holding each half in the folded towel, scoop the pulp out of the skin into a food mill. Discard the skin. Puree through the food mill fitted with a fine blade, or in a food processor. With a whisk (or in the food processor), stir in the cream, 4 tablespoons of the butter, the brown sugar, cinnamon, nutmeg, and ginger. Beat until thoroughly combined. Season to taste with salt and white pepper. Cover the bowl and keep the sweet potatoes warm over a pan of simmering water if serving right away.
Put the remaining 4 tablespoons butter in a small saucepan over medium heat. Melt the butter and then swirl the pan continuously over the heat until the butter turns nut-brown and fragrant. Remove from the heat and stir in the hazelnuts and optional thyme or marjoram.
Transfer the sweet potatoes to a serving dish and drizzle the hazelnut butter over them. Serve immediately.
Wolfgang Puck