Spiced Sweet Potato Gratin

Preparation Preheat oven to 350°F. Cook sweet potatoes in large pot of boiling salted water until just tender, about 20 minutes (do not overcook). Drain well and cool. Peel sweet potatoes; cut into 1/4-inch-thick slices. Mix curry powder, cumin, cinnamon, ginger, and salt in small bowl to blend. Completely line bottom of 9-inch-diameter springform pan with sweet potato slices, filling in any spaces with cut-up sweet potato slices. Press down lightly. Spread 1/2 cup sour cream over sweet potatoes. Sprinkle 1 tablespoon spice mixture over sour cream. Sprinkle with 1 cup cheese. Repeat twice with remaining sweet potatoes, sour cream, spice mixture, and cheese. Place pan on rimmed baking sheet; bake until cheese is melted and sweet potatoes are heated through, about 40 minutes. DO AHEAD Can be made 8 hours ahead. Cover and chill. If desired, reheat in 400°F oven until hot, about 15 minutes. Remove pan sides from gratin; cut into wedges. Serve gratin warm or at room temperature.

Preparation Preheat oven to 350°F. Cook sweet potatoes in large pot of boiling salted water until just tender, about 20 minutes (do not overcook). Drain well and cool. Peel sweet potatoes; cut into 1/4-inch-thick slices. Mix curry powder, cumin, cinnamon, ginger, and salt in small bowl to blend. Completely line bottom of 9-inch-diameter springform pan with sweet potato slices, filling in any spaces with cut-up sweet potato slices. Press down lightly. Spread 1/2 cup sour cream over sweet potatoes. Sprinkle 1 tablespoon spice mixture over sour cream. Sprinkle with 1 cup cheese. Repeat twice with remaining sweet potatoes, sour cream, spice mixture, and cheese. Place pan on rimmed baking sheet; bake until cheese is melted and sweet potatoes are heated through, about 40 minutes. DO AHEAD Can be made 8 hours ahead. Cover and chill. If desired, reheat in 400°F oven until hot, about 15 minutes. Remove pan sides from gratin; cut into wedges. Serve gratin warm or at room temperature.