Sweet and White Potato Casserole

3 cups thinly sliced yellow onions

2 bay leaves

4½ cups thinly sliced, peeled Yukon Gold potatoes

4½ cups thinly sliced, peeled sweet potatoes

2 tablespoons unsalted butter

7 tablespoons all-purpose, unbleached flour

1 teaspoon salt

½ teaspoon ground mustard

½ teaspoon fresh ground black pepper

½ teaspoon sweet paprika, plus more for garnish (or smoked paprika)

1½ low-fat milk

2 cups fat-free half-and-half

4 tablespoons chopped fresh parsley leaves (Italian flat-leaf preferred)

1 teaspoon minced fresh thyme leaves

Place oven rack in the center position and heat oven to 400 degrees. Lightly spray a 13-by-9-inch casserole dish with vegetable oil. Set aside.

Bring a large pot of salted water to the boil. Add bay leaves, onions and potatoes and boil, covered, for 5 minutes. Drain; discard bay leaves.

Meanwhile, place a 2-quart saucepan over low heat and add butter. When it melts, stir in flour, salt, mustard, pepper and paprika. Whisk in milk and half-and-half and cook, whisking constantly, until smooth and thickened (add more milk if too thick). Remove from the heat, whisk in parsley and thyme; set aside.

In the prepared casserole, arrange one-third of the potatoes and onions; pour over one-third of sauce. Repeat with half of remaining potatoes and onions, and half of remaining sauce. Top with remaining potatoes and sauce. Dust generously with paprika (if you use smoked paprika dust with a lighter touch). Bake, uncovered 35 minutes or until tender and the top browns slightly.

Serves 10.

Nutrition values per serving: 202 calories (16.3 percent from fat), 3.7 g fat (1.9 g saturated), 36.8 g carbohydrate, 7.7 g protein, 9.7 mg cholesterol, 291 mg sodium.