Place chicken breasts in a 9x13” baking dish.
Sprinkle generously with salt and pepper.
Bake chicken breasts at 350° for about 40-45 minutes or until done.
Cut in bite sized pieces.
Place in greased 10-x15 baking dish.
Meanwhile, cook rice.
Add 3 cups of water to rice and heat to boiling.
Lower heat and simmer until done—about 25-30 minutes.
Add to chicken in baking dish.
Steam broccoli about 3 minutes in microwave in microwavable steamer.
Drain.
Sprinkle lemon juice over top.
Add to dish with chicken and rice.
In a large skillet, melt butter over medium heat.
Add onions, celery, mushrooms and garlic and sauté a few minutes until translucent.
Stir half of a 12-oz. can of evaporated milk with the gluten free flour.
Whisk to combine.
Add to onion mixture and stir to combine.
Add remaining milk and whisk until incorporated.
Add salt, pepper and 3 ½ cups cheese.
Stir and heat a few minutes until cheese melts.
Add cheese mixture to other ingredients in baking dish and stir to combine.
Add cream to make of better spreading consistency.
Top with remaining ½ cup cheddar cheese.
Cover and bake at 350° for about 30 minutes or until casserole is heated through and bubbly.