Macaroni and Cheese and Broccoli Casserole

Name: Macaroni-and-Cheese (and Broccoli) Casserole
Ingredients: 1 cup chicken stock (or vegetable stock or water); 2 cups whole milk; 1/2 cup all-purpose flour; 1 tablespoon salted butter; 3 cups grated sharp cheddar cheese; 1/2 cup ricotta cheese; 1/4 cup grated Parmesan cheese; 1 pound elbow macaroni; 1 generous head of broccoli, cut into florets and stems peeled and sliced; 2 tablespoons toasted bread crumbs; 2 tablespoons olive oil