Broccoli Chicken Casserole

3 heads broccoli (can use stalks as well), chopped
1 cup chicken broth
1 medium onion, chopped
2 stalks celery, chopped
1 tsp minced garlic
2 Tbsp butter
3 Tbsp flour
1 tsp salt
1 cup milk
1 Tbsp Dijon mustard
2 cups shredded Cheddar cheese, divided
1/2 lb chicken thighs, chopped
3 cups cooked brown rice (1 cup uncooked)

1. Place chopped broccoli and chicken broth in a pot. Cover and cook over medium-high heat until broccoli is crisp-tender. Set aside.
2. In a large skillet, saute onions, celery, and garlic in butter, until onions and celery are soft. Add chicken and cook until no longer pink. After chicken is cooked, add flour and salt and stir for about one minute. Add 1 cup milk and stir until thickened. Add mustard and 1 cup cheddar cheese and stir to combine.
3. Add cooked broccoli (with liquid) to skillet with the chicken. Stir to combine.
4. Spread cooked rice in bottom of 2 1/2 quart casserole dish. Sprinkle 1/2 cup cheese over rice. Add broccoli/chicken mixture, and sprinkle with remaining cheese. Bake at 350 for 20 minutes, or until sauce is bubbly.

Source: Me!