01 -
Pour half the marinara sauce into the base of a 6-litre or larger slow cooker and set aside.
02 -
In a large mixing bowl, whisk the eggs to break them up. Add panko, Parmesan, onion, parsley or basil, garlic, salt, oregano, and black pepper. Stir until evenly combined.
03 -
Add the ground chicken to the bowl. Using clean hands, gently mix until combined, taking care not to overwork the mixture.
04 -
Fill a medium bowl with water. Form the mixture into 1.5-inch (about 4-cm, 2 tablespoon) meatballs, wetting your hands as needed to prevent sticking. Place each meatball directly into the sauce in the slow cooker. Arrange in roughly 1.5 layers.
05 -
Pour the remaining marinara sauce evenly over the formed meatballs.
06 -
Cover and cook on the LOW setting for 6–8 hours, until meatballs are fully cooked through and flavors have developed.
07 -
In the final 15 minutes, sprinkle meatballs with mozzarella cheese, cover, and continue cooking until melted, if desired.
08 -
Top with additional fresh parsley or basil and extra Parmesan before serving.