From Bon Appétit January 2009
Nonstick vegetable oil spray
6 tablespoons (3/4 stick) butter, melted, divided
1 1/4 pounds russet potatoes (about 2 medium), peeled, cut into scant 1/8-inch-thick rounds
1/2 3-inch-diameter celery root (celeriac), trimmed, peeled, halved, very thinly sliced (1 1/4 cups to 1 1/2 cups)
1 medium turnip, peeled, halved, very thinly sliced (1 1/4 cups to 1 1/2 cups)
1 teaspoon chopped fresh rosemary
1. Spray 9 1/2-inch-diameter nonstick oven-proof skillet with vegetable oil spray; add 2 tablespoons melted butter. Arrange half of potato rounds in skillet, overlapping in concentric circles. Sprinkle lightly with salt and pepper. Alternate celery root slices and turnip slices atop potatoes in overlapping concentric circles. Sprinkle with rosemary, then lightly with salt and pepper. Drizzle with 2 tablespoons melted butter. Top with remaining potato slices in overlapping concentric circles. Sprinkle lightly with salt and pepper. Press with spatula to compact.
2. Preheat oven to 400°F. Cook vegetables over medium heat 5 minutes. Reduce heat to medium-low; cover and cook until bottom layer is golden, about 25 minutes. Uncover and drizzle with 2 tablespoons melted butter. Transfer skillet to oven; bake uncovered until vegetables are very tender and golden, 20 to 25 minutes.
3. Run small knife around vegetables to loosen from skillet. Place large platter atop skillet. Using pot holders, firmly hold skillet and platter together and invert vegetables onto platter. Cut into wedges and serve.