In a large mixing bowl, combine ground chicken, panko breadcrumbs, eggs, chopped onion, minced garlic, chopped parsley, salt, and pepper. Mix until just combined.

Roll the mixture into approximately 24 meatballs and place them on a foil-lined baking sheet.

Preheat the broiler and broil the meatballs for about 6 minutes on one side and then flip and broil for another 6 minutes.

Transfer the cooked meatballs to the slow cooker.

In a separate bowl, whisk together buffalo sauce, light brown sugar, and soy sauce, then pour over the meatballs.

Set slow cooker to low heat and cook for about 2 hours.

Gently stir the meatballs before serving and garnish with chopped parsley and crushed red pepper flakes if desired.