Creamy Au Gratin Potatoes

4 (10) russet potatoes, sliced (I use the food processor)
1/2 (1) onion, sliced into rings and then slice the rings in halves or fourths
salt and pepper to taste
3 tablespoons (1/3 cup plus 3T) butter
3 tablespoons (1/3 cup plus 2T) flour
1/2 teaspoon (1 1/4 teaspoon) salt
2 cups (5 cups) milk
1 1/2 cups (3 3/4 cups) shredded Cheddar cheese

The measurements in parenthesis are for 10 servings; the first are for four servings. I always make lots.

Preheat oven to 400 degrees.

Layer 1/2 of the potatoes into bottom of the casserole dish (I need to use 2-3 dishes when I make the large amount). Top with the onions slices, and add the remaining potatoes. Season with salt and pepper to taste.

In a medium-sized saucepan, melt butter over medium heat. Mix in the flour and salt, 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 1/2 hours at 400 degrees.

Enjoy! I have made this for the past two Easters and everyone seems to really like it. I wish I had taken a picture of it before we dashed out the door on Easter! It looked nice in my red casserole dishes.