2 ¾ cups 1% milk, divided
¼ cup half-and-half
½ large onion, peeled and thinly sliced
1 bay leaf
5 whole peppercorns
12 ounces elbow macaroni
3 tablespoons cornstarch
½ teaspoon dry mustard
1 ½ cups finely shredded reduced-fat extra sharp cheddar cheese(white or yellow)
1 tablespoon freshly grated Parmesan cheese
1 teaspoon salt
½ teaspoon fresh ground black pepper

Topping ingredients:

¾ cup fresh breadcrumbs (preferably made from Italian bread, but whole-wheat bread is fine)
2 teaspoons olive oil