Start by preheating your oven to 400°F (200°C) if you plan to bake the meatballs. If frying, you can skip this step. Prepare your baking sheet by lightly greasing it with olive oil or lining it with parchment paper.
In a large mixing bowl, combine the ground chicken, breadcrumbs, grated Parmesan cheese, chopped basil, minced garlic, egg, salt, and black pepper. Use your hands or a spatula to mix everything together until just combined. Be careful not to overmix, as this can lead to tough meatballs.
With clean hands, scoop a portion of the mixture and roll it into a ball, about 1.5 inches in diameter. Place the formed meatballs on a greased baking sheet or a plate if frying. Repeat until all the mixture is shaped into meatballs.
If you’re frying, heat a couple of tablespoons of olive oil in a skillet over medium heat. Once the oil is hot, add the meatballs in batches, ensuring not to overcrowd the pan. Cook for about 6-8 minutes, turning occasionally until browned on all sides and cooked through. If baking, place the meatballs in the preheated oven and bake for 20-25 minutes or until they reach an internal temperature of 165°F (75°C).
Once the meatballs are cooked, pour the marinara sauce over them in the skillet or transfer them to a baking dish if baked. Sprinkle the shredded mozzarella cheese on top. If you’re using the skillet, cover it with a lid. If you're in the oven, return the dish to bake for another 5-10 minutes until the cheese is melted and bubbly.
Remove the meatballs from the heat and let them cool slightly. Serve them warm, garnished with additional fresh basil if desired. Enjoy with pasta, in a sub, or simply on their own!