Preheat the oven to 375°F and position the rack in the top third of the oven.
In a large mixing bowl, combine the ground chicken, egg, panko breadcrumbs, half of the parmesan cheese, Italian seasoning, garlic powder, onion powder, salt, and pepper. Mix everything together until well combined, but avoid overworking the mixture. It will be quite moist. Form the mixture into 1-inch meatballs (about 20 meatballs) and arrange them on a parchment-lined baking sheet for easy cleanup.
Heat the olive oil in an oven-safe skillet over medium-high heat for a few minutes. Cook the meatballs in two batches, browning them on all sides for about 5 minutes per batch. Use tongs to turn the meatballs quickly, as they will brown quickly. If necessary, add a little more olive oil to the pan for the second batch. Once browned, remove the meatballs from the skillet and set them aside.
If there is too much excess oil in the skillet, drain it, but be sure to leave the browned bits. Remove the skillet from the heat for a couple of minutes to cool slightly before adding the marinara sauce (this prevents splattering).
Pour the marinara sauce into the skillet, then return the meatballs to the pan, arranging them evenly. Sprinkle the remaining parmesan cheese and the shredded mozzarella over the top of the meatballs.
Transfer the skillet to the oven and bake for 15 minutes, until the meatballs are fully cooked. If desired, broil for a couple of minutes to brown the cheese (watch closely to avoid burning).