Spiced Sweet Potato Gratin

Ingredients

• 1 tablespoon curry powder 
• 0.8 teaspoon ground cinnamon 
• 1 tablespoon ground cumin 
• 0.8 teaspoon ground ginger 
• 4 pounds red-skinned sweet potatoes 
• 0.5 teaspoon salt (scant)
• 1.5 cups cup heavy whipping cream sour divided
• 12 ounces cheddar shredded white extra-sharp

Equipment

• bowl
• frying pan
• baking sheet
• oven
• pot
• springform pan

Directions

1. Preheat oven to 350°F. Cook sweet potatoes in large pot of boiling salted water until just tender, about 20 minutes (do not overcook).
2. Drain well and cool. Peel sweet potatoes; cut into 1/4-inch-thick slices.
3. 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.
4. Spread 1/2 cup sour cream over sweet potatoes.
5. Sprinkle 1 tablespoon spice mixture over sour cream.
6. Sprinkle with 1 cup cheese. Repeat twice with remaining sweet potatoes, sour cream, spice mixture, and cheese.
7. 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.
8. Remove pan sides from gratin; cut into wedges.
9. Serve gratin warm or at room temperature.