4 tablespoons unsalted butter
2 sweet potatoes, peeled and thinly sliced (about 1-1/2 pounds)
3 Russet potatoes, peeled and thinly sliced (about 1-1/2 pounds)
1 teaspoon dried thyme leaves
1 teaspoon salt
1/4 teaspoon ground black pepper
1 medium-sized leek, trimmed, quartered and white part finely chopped (about 1 1/4 cups)
1/4 cup grated Parmesan cheese
Preheat oven to 425 degrees F. Melt 1 tablespoon butter in 8-inch ovenproof nonstick skillet over medium heat. Swirl pan to coat bottom and sides; set aside.
Toss sweet potatoes with 1-1/2 tablespoons butter, 1/2 teaspoon thyme, 1/2 teaspoon salt and 1/8 teaspoon pepper in medium bowl. Set aside.
Toss Russet potatoes with remaining butter, thyme, salt and pepper in second bowl.
Place one layer of Russet potatoes in overlapping circles on bottom of skillet. Sprinkle with leeks, and top with layer of sweet potatoes. Sprinkle with 1 tablespoon Parmesan. Repeat layering, ending with layer of sweet potato slices.
Place skillet on burner. Cook potatoes 5 minutes over medium heat to brown bottom. Transfer skillet to oven, and bake 45 to 50 minutes, or until potatoes are tender and beginning to brown. Set 9-inch plate on top of skillet. Flip upside down to unmold potatoes. Slice into wedges, and serve.
Per Serving: cal. (kcal) 199, Fat, total (g) 7, chol. (mg) 18, sat. fat (g) 4, carb. (g) 31, fiber (g) 4, sugar (g) 9, pro. (g) 4, sodium (mg) 412, Percent Daily Values are based on a 2,000 calorie diet