The box of instant au gratin potatoes from the supermarket advertises a dish “made with 100 percent real cheese and potatoes.” But the potatoes are dehydrated and the cheese sauce is powdered. No thanks.

On the flip side, homemade au gratin can drown out the positive nutritional value of potatoes with heavy cream and cheddar cheese.

So what's a conscientious cook to do?

This Au Gratin Potato Casserole uses reduced-fat dairy products to trim the fat and calories from this creamy, satisfying comfort food that few of us would be willing to banish from the dinner table.

Au Gratin Potato Casserole

Makes 12 servings

2 pounds red-skinned potatoes, not peeled (about 5 to 6 medium)

1/4 cup chopped onion

2 cloves garlic, minced

2 tablespoons flour

11/2 cups fat-free skim milk

1/8 teaspoon salt

1/8 teaspoon pepper

2 tablespoons minced flat-leaf (Italian) parsley, minced, divided

1 cup reduced-fat shredded cheddar cheese

2 tablespoons shredded Parmesan cheese

Scrub potatoes and remove eyes. Cut larger potatoes in half. Place potatoes in large saucepan and add cold water to cover. Cover pan and heat over high heat until water boils. Reduce heat and cook until potatoes are tender, about 30 to 40 minutes. Drain potatoes; cool slightly.

Preheat oven to 350 degrees. Spray an 11-by-7-inch (2-quart) casserole dish with nonstick spray coating.

Combine onion, garlic, flour, milk, salt and pepper in a medium, heavy saucepan. Whisk thoroughly, blending until the flour is completely dissolved. Heat over medium- low heat, whisking constantly, until milk is bubbly and slightly thickened. Remove from heat. Whisk in 1 tablespoon parsley and the cheddar cheese; stir until cheese is blended.

When potatoes are just cool enough to handle, peel and slice 1/4-inch thick. Place sliced potatoes in prepared casserole dish. Drizzle cheese sauce over potatoes, covering slices evenly and completely. Sprinkle with Parmesan cheese. Bake 20 to 30 minutes or until hot and golden. Sprinkle with remaining parsley just before serving.