3 tablespoons butter 
3 tablespoons all-purpose flour 
1-1/2 teaspoons salt 
1/8 teaspoon pepper 
2 cups 2% milk 
1 cup shredded cheddar cheese 
5 cups thinly sliced peeled potatoes (about 6 medium) 
1/2 cup chopped onion 
Additional pepper, optional
1. Preheat oven to 350°. In a large saucepan, melt butter over low heat. Stir in flour, salt and pepper until smooth. Gradually add milk. Bring to a boil; cook and stir 2 minutes or until thickened. Remove from heat; stir in cheese until melted. Add potatoes and onion. 
2. Transfer to a greased 2-qt. baking dish. Cover and bake 1 hour. Uncover; bake 30 to 40 minutes or until the potatoes are tender. If desired, top with additional pepper.
TOTAL TIME: Prep: 20 min. Bake: 1-1/2 hours 
YIELD: 8 servings. 
These homemade au gratin potatoes are always welcome at our dinner table, and they're so simple to make. A perfect complement to ham, this homey potato gratin also goes well with pork, chicken and other entrees. 
Nutrition Facts
3/4 cup: 224 calories, 10g fat (7g saturated fat), 35mg cholesterol, 605mg sodium, 26g carbohydrate (4g sugars, 2g fiber), 7g protein.