Light Scalloped Potatoes

1 cup skim milk
1 Tbs. cornstarch
1/2 tsp salt
1/4 tsp. white pepper
2 medium baking potatoes, scrubbed well and cut crosswise into 1/8-inch slices (do not peel)
1 medium onion, peeled and sliced thin

Combine milk and cornstarch in a saucepan and whisk until smooth. Bring to a boil, lower heat, and stirring continuously, cook until thickened, about 3-5 minutes.
1. Preheat oven to 350 degrees. Coat shallow casserole with vegetable spray.
2. Layer half of the sauce, half the potatoes, all of the onions, the remaining potatoes, and ending with remaining sauce in the casserole.
3. Cover and bake 40 minutes. Uncover and bake until golden brown and bubbly, about 20 more minutes.