In a spacious mixing bowl, combine the ground chicken with breadcrumbs, grated Parmesan cheese, chopped parsley, beaten egg, minced garlic, onion powder, salt, and black pepper. Use your hands or a spoon to mix until the ingredients are evenly incorporated, ensuring not to overmix.
Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper to prevent sticking.
Using your hands, form the chicken mixture into meatballs, aiming for a size of about 1 to 1.5 inches in diameter. Place each meatball on the prepared baking sheet, spacing them evenly apart.
In a large skillet, heat the olive oil over medium heat. Add the meatballs in batches, being careful not to overcrowd the pan. Cook for approximately 3-4 minutes, turning them occasionally, until browned and crisp on all sides. Once browned, remove the meatballs from the skillet and transfer them to the baking sheet.
Once all the meatballs are browned, place the baking sheet in the preheated oven. Bake for about 10-15 minutes, or until the internal temperature of the meatballs reaches 165°F (75°C) using a meat thermometer.
While the meatballs are baking, prepare the garlic butter sauce in the same skillet used for the meatballs. Lower the heat to medium-low, then add the butter. Once melted, introduce the minced garlic and lemon zest, cooking for about 2 minutes until fragrant, stirring frequently to prevent burning.
When the meatballs have finished baking, transfer them to the skillet with the garlic butter sauce. Gently toss the meatballs in the sauce for about 1-2 minutes to ensure they are well-coated and absorb the flavors.
Serve your garlic butter chicken meatballs warm, garnished with a sprinkle of fresh parsley on top for a pop of color and flavor.