Chicken and broccoli

CHICKEN BROCCOLI CHEESE CASSEROLE
1 lb cooked chicken, shredded Note: if you don’t have any cooked chicken on hand it is very simple to poach chicken breasts. Place the chicken in a large skillet with about 2 cups of water. Bring to boiling; reduce heat. Simmer, covered, for 12-14 minutes or until chicken is no longer pink (170 degrees). Drain well. Shred chicken.
1 cup cooked brown rice (cooking the rice in gluten free chicken broth works nicely)
1 lb fresh broccoli, chopped
2 Tablespoons of butter
2 Tablespoons of brown rice flour
1/2 teaspoon salt
1/4 teaspoon of pepper
1/2 teaspoon of dried mustard
1 1/2 cups of milk
1 Tablespoon of plain greek yogurt  (optional)
1 1/2 cups of cheddar cheese, shredded
1/2 cup gluten-free bread crumbs for topping

Directions:
Melt the butter in a medium saucepan. Add the flour, salt, pepper, and mustard, and cook 2-3 minutes until bubbly and foamy. Slowly whisk in the milk and cook until thickened. Stir in the shredded cheese. Place the brown rice, chicken, and broccoli in a casserole dish and pour the white sauce over the top. Add the mayonnaise and lemon juice if using and mix until combined. Spread the breadcrumbs and slivered almonds over the top. Bake uncovered for about 30 minutes at 350 degrees.