Warm-up a medium saute pan over medium-high heat. Add the chopped onions and garlic, along with a good dose of salt and pepper. Cook the onions and garlic for 5 to 7 minutes, or until the onions become transparent. Remove the pan from the heat and set it aside to cool slightly.
While the onions cool, combine the ground chicken, Parmesan cheese, parsley, eggs, and breadcrumbs in a large mixing dish. Squish the ingredients together with your hands to combine them. Mix in the onion mixture. (Reserve the saute pan for subsequent use in heating the sauce.) Squish in the onion mixture with your hands.
Add 1/2 cup water and a generous pinch of Kosher salt and ground black pepper to taste. Squish everything together one more time. This is a crucial phase. The mixture should be pretty wet, which will result in moist and delicious meatballs.
Roll the meatball mixture into little golf-ball-sized balls. Place each one on a prepared baking sheet, leaving space between each one.
Bake the meatballs for 25–30 minutes.
With about 10 minutes remaining in the baking time, place your sauce in a saute pan and cook it over medium-low heat. Remove the meatballs from the sheet pan and drop them in the warm sauce.
Spoon the warm sauce over the meatballs and heat for a minute or two to allow the sauce to soak.
Serve the delectable meatballs with zoodles, whole wheat pasta, or brown rice, as desired. Top with more sauce, Parmesan cheese, and parsley.