Three Potato Gratin

Directions

1. 1
   Preheat oven to 350 degrees.
2. 2
   Thoroughly grease 2 quart casserole dish.
3. 3
   In a saucepan melt the butter and whisk in flour to make a roux. Cook for about one minute. Add salt, pepper, sour cream and milk. Gradually stir over medium heat to keep the mixture from burning. Stir until thick, about 2-3 minutes, then add parmesan cheese.
4. 4
   Arrange half of potatoes in casserole dish, making sure they overlap. Pour half of the cheese mixture over potatoes, then repeat the process.
5. 5
   Bake covered for 35 to 40 minutes, then uncover and bake additional 15 minutes.
6. 6
   Top with shredded cheddar and cook another 5 - 10 minutes until cheese is melted and bubbly. Make sure potatoes are cooked through. Test by inserting knife - it it goes in and comes out easily and cleanly casserole is done.