Cook rice in chicken broth with diced onion or dried onion. Steam (microwave) broccali and mushrooms for 2-3 minutes in large bowl. After steaming, add cooked chicken, soup, half and half, 1 cup cheddar cheese, salt, pepper, sherry, garlic salt, rice. Mix all together, pour in casserole dish. Sprinkle 1/2 cup cheddar cheese on top along with panko crumbs. Bake covered at 350 for 30 minutes, raise to 375 and bake uncovered for 15 more minutes. If the top is not browned as you like it, broil for 2-3 minutes.