Potato and Ground Beef Gratin - Legendary Recipes %

Ingredients

• 1 lb lean (at least 80%) ground beef
• 1 teaspoon salt
• 1/2 teaspoon pepper
• 3 tablespoons butter or margarine
• 1 small onion, chopped (1/4 cup)
• 3 tablespoons all-purpose flour
• 2 teaspoons chopped fresh thyme leaves
• 3 cups milk
• 3 cups shredded mild Cheddar cheese (12 oz)
• 6 medium white potatoes (2 1/2 lb), peeled, thinly sliced (6 cups)