country potatoes au gratin

I got this recipe from cookinglight.com
this is my modified recipe these were really good.


Ingredients
1 teaspoons butter
1 medium onion (about 5 1/2 ounces), thinly sliced
3 garlic cloves, minced
2 cups 2% reduced-fat milk
1 teaspoon salt
1/4 teaspoon freshly ground black pepper
1/3 ounces all-purpose flour (about 2/3 cup)
3 ounces shredded sharp cheddar cheese (1 1/2 cups), divided
6 ounces diced ham (about 1 1/4 cups) (omitted)
1 1/2 pounds peeled baking potatoes, cut into 1/8-inch-thick slices
1 T brown mustard
Cooking spray

Preparation
Preheat oven to 350°.
Melt butter in a Dutch oven over medium-high heat. Add onion and garlic; sauté 5 minutes or until onion is tender. Combine milk, salt, pepper, and flour, stirring with a whisk. Add milk mixture to pan. Bring to a simmer; cook until slightly thick (about 2 minutes), stirring frequently. Add 4 ounces cheese and ham, stirring until cheese melts. Stir in potatoes.
Place the potato mixture in a 13 x 9-inch baking dish coated with cooking spray. Sprinkle potato mixture with remaining 2 ounces of cheese. Cover with foil coated with cooking spray. Bake at 350° for 45 minutes. Uncover and bake an additional 30 minutes or until lightly browned and potatoes are tender. Let stand 15 minutes before serving