Barley and vegetables may be made the day before.
Bring stock, garlic powder and barley to a boil. Reduce heat to simmer, cover and cook for 40 minutes. (Leave any remaining liquid to be absorbed while baking.) Transfer to a large casserole dish and add the tomato sauce. Preheat the oven to 350°F. Sauté the mushroom, onion, pepper and spinach in olive oil while the barley is cooking and add to the casserole. Stir in the chicken and ricotta and top with mozzarella cheese. Bake covered with foil for 30 minutes. Note: To save on meal preparation time, cook the barley and veggies the day before. Stir in tomato sauce. Set aside in casserole dish in refrigerator. One hour before meal time take the dish out and bring to room temperature, stirring a few times. Preheat the oven to 350°F. Stir in the chicken and ricotta and top with mozzarella cheese. Bake covered with foil for 30 minutes until warmed through.