Perfect Au Gratin Potatoes

The creamy cheese sauce and the tender potatoes
in this classic French dish combine to make a
deliciously addictive experience.
This is exactly how I have made my au gratins all my life.
There is a difference between au gratin and scalloped potatoes.
If there is cheese in them, they are au gratin,
with plain white sauce they are scalloped.

Ingredients:
4 russet potatoes, sliced into 1/4 inch slices
1 onion, sliced into rings
salt and pepper to taste
3 tablespoons butter
3 tablespoons all-purpose flour
1/2 teaspoon salt
2 cups milk
1 1/2 cups shredded Cheddar cheese

Directions:
Preheat oven to 400 degrees F.
Butter a 1 quart casserole dish.
Layer 1/2 of the potatoes into bottom
of the prepared casserole dish.
Top with the onion slices,
and add the remaining potatoes.
Season with salt and pepper to taste.
3.In a medium-size saucepan,
melt butter over medium heat.
Mix in the flour and salt,
and stir constantly for one minute.
Stir in milk. Cook until mixture has thickened.
Stir in cheese all at once,
and continue stirring until melted, about 30 to 60 seconds.
Pour cheese over the potatoes,
and cover the dish with aluminum foil.
Bake 1 1/2 hours in the preheated oven.