Au Gratin Potatoes

Potatoes + cheese = delicious! These were surprisingly easy to make, but they do take awhile to cook, so you definitely have to plan in advance to make them. We didn't have any cheddar cheese though, so I used 3 slices of Muenster and 3 slices of Colby.

4 russet potatoes, sliced thin
1 onion, chopped
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

Preheat oven to 400 degrees Fahrenheit. Butter a 1 quart casserole dish. Mix together the potatoes and onions and place in the prepared casserole dish. Season with salt and pepper to taste. In a medium-size saucepan, melt butter over medium heat. Mix in the flour and salt, and stir constantly with a whisk 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 - 1-1/2 hours in the preheated oven.