Instructions

1. Heat oven to 375°F. Melt 2 teaspoons butter in large nonstick skillet over medium heat. Add onion and thyme; cook and stir 3 to 4 minutes or until onion is tender. Remove from heat; stir in corned beef and horseradish-butter mixture. Meanwhile, coat bottom and sides of 9-inch glass pie plate with remaining 1 teaspoon butter; set aside.
2. Cut each potato half into 4 wedges. Arrange 1/2 of potato wedges in single layer over bottom of pie plate; stick remaining potato wedges upright around the edge of the pie plate. Combine cheeses in small bowl. Sprinkle potatoes with 1/2 of cheese mixture. Top with corned beef mixture and remaining cheese mixture. Press firmly with spatula to compact layers; cover with aluminum foil.
3. Bake in 375°F oven 25 to 30 minutes or until heated through. Uncover; continue baking 3 to 5 minutes or until cheese is melted and edges begin to brown. Let stand 5 minutes. Cut into wedges. *If using deli corned beef and frozen prepared roasted potatoes, increase covered baking time to 35 minutes.