Step 1

Bring the marinara sauce to a simmer over medium heat in a 10 or 12-inch cast iron or oven-safe skillet. Meanwhile, place the chicken, 1/2 cup of the breadcrumbs, half of the Parmesan cheese, parsley, egg, garlic, salt, oregano, and black pepper in a large bowl. Mix lightly with a fork until just combined.

Step 2

When the sauce is simmering, form the meat mixture into 1 1/2-inch wide meatballs (about 2 tablespoons each), wetting your hands with water as needed to keep the mixture from sticking, and carefully drop the meatballs into the sauce in a single layer as you go.

Step 3

Cover and simmer gently, flipping the meatballs over halfway through cooking, until cooked through, 20 to 25 minutes total. Meanwhile, arrange a rack 6-inches from the broiler and heat to broil. Combine the remaining 1/2 cup breadcrumbs, olive oil, and a pinch of salt in a small bowl; set aside.

Step 4

Uncover and sprinkle the mozzarella evenly over the meatballs. Sprinkle with the breadcrumb mixture and remaining Parmesan cheese. Broil uncovered until the cheese is melted and bubbly and the breadcrumbs are golden-brown, 3 to 5 minutes. Sprinkle with the herbs and serve.