Preheat oven or grill to 350 degrees.
Spray baking dish or skilet with nonstick cooking spray, set aside. Cook pasta according to package directions.
In a large, heavy skillet melt butter. Whisk in flour to combine. Slowly add milk, whisking to combine. Whisk in sour cream and seasonings. Add cheeses, reserving 1 cup cheddar cheese for topping, and whisk until melted.
In a small bowl, beat eggs. Whisk in a small amount of the cheese mixture. Add egg mixture to the mixture in skillet and whisk to combine.
Stir in the cooked and drained pasta. Mix well and pour into a buttered cast iron skillet or casserole dish. Top with reserved shredded cheese.
Bake in oven or grill for 30 to 40 minutes, or until hot and bubbly.
Serve warm.
