Mix ground chicken, spinach, mozzarella, parmesan, egg, and onion in large bowl
Spray large muffin pan with non stick spray or use silicon muffin pan
Fill each cup halfway full with mixture
In medium bowl, mix all sauce ingredients together
Spoon over meatloaf cups leaving a little for serving
Cook cups for 45-50 minutes or until cooked through
Top with remaining sauce and serve hot
Please note that I am not a certified nutritionist. Any nutritional information that is discussed or disclosed in this post should only be seen as my best amateur estimates. If nutrition is important to you, I highly encourage you to verify any data you see here with your favorite nutrition calculator.