Au Gratin Potatoes

6-8 russet potatoes

2 onions

4 tbls butter

4 tbls flour

salt

2 cups milk

1.5 cups cheddar cheese

Slice onion and potatoes into 1/4-1/8" slices.  Grease a casserole dish and layer the potatoes and onion is the dish.

Season with salt and pepper.  In a saucepan melt butter and stir in flour and salt to make a rue whisking constantly for 2 minutes.  Stir in milk and cook until mixture has thickened.  It's important to use a low to medium heat when adding flour so it doesn't turn into cement.  Stir in all the cheese at once and continue to stir constantly until it has all melted.  Pout mixture over potatoes and bake at 400 for 1.5 hours.  You may cover with a lid or foil for the first 45 minutes if you wish.