One of the South's prized crops, sweet potatoes have dozens of varieties from white to deep orange. Look for smooth, unblemished medium-size potatoes. Store in a cool, dark place, but do not refrigerate as that will cause them to harden in the center. To prevent the flesh from browning, rinse cut sweet potatoes in cold water before cooking. Cubes of French bread are baked in a rich Parmesan custard with smoky bacon, spinach, and chunks of roasted sweet potatoes. Serve this comforting casserole with a green salad for dinner or as a company-worthy brunch.