- 3 large boneless chicken breasts
- 2 (14 ounce) cans cream of mushroom soup
- 1 cup mayonnaise
- 1 (16 ounce) bag steam-in-bag partially cooked frozen broccoli
- 1 onion, diced
- 8 fresh mushrooms, or more to taste, sliced (optional)
- 3 cups shredded Cheddar cheese, or more to taste
- 2 cups cooked rice
- Bring a large saucepan of lightly salted water to a boil. Cook chicken in boiling water until no longer pink in the center and the juices run clear, about 30 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Remove chicken to a cutting board to cool. Shred cooled chicken into strands.
- Preheat oven to 400 degrees F (200 degrees C).
- Steam broccoli in microwave oven until tender-crisp, 4 to 6 minutes or according to package directions.
- Stir mushroom soup and mayonnaise together in a bowl; add broccoli, onion, and mushrooms and stir to coat.
- Spread cooked rice into the bottom of a casserole dish. Top rice with shredded chicken. Spread the mushroom soup mixture over the chicken. Sprinkle Cheddar cheese over everything.
- Bake in preheated oven until slightly browned on top, 35 to 45 minutes.