Never-Fail Scalloped Potatoes Recipe

Ingredients

• 2 tablespoons butter
• 3 tablespoons all-purpose flour
• 1 teaspoon salt
• 1/4 teaspoon pepper
• 1-1/2 cups fat-free milk
• 1/2 cup shredded reduced-fat cheddar cheese
• 2 pounds potatoes, peeled and thinly sliced (about 4 cups)
• 1 cup thinly sliced onions, divided