Saucy Scalloped Potatoes

Ingredients

• 4 cups thinly sliced peeled potatoes (about 2 pounds)
• 1 can (10-3/4 ounces) condensed cream of celery soup or mushroom soup, undiluted
• 1 can (12 ounces) evaporated milk
• 1 large onion, sliced
• 2 tablespoons butter
• 1/2 teaspoon salt
• 1/4 teaspoon pepper
• 1-1/2 cups chopped fully cooked ham