Boil a large pot of water. Add a generous pinch of salt, then add pasta and cook for 5 minutes, or about half of the time recommended on the package directions. It should still be very firm; it will continue softening in the oven. Drain and set aside.

To make the meatballs, combine the ground chicken, 1/2 cup breadcrumbs, 1/3 cup Parmesan, egg, 1 teaspoon Italian seasoning, 1/2 teaspoon garlic powder, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper in a large bowl. Stir with a fork until evenly combined, then portion and roll into into small meatballs, about 1” diameter each.

Preheat oven to 350 degrees F.

Warm a generous slick of olive oil in a large oven-safe skillet over medium-high heat. Brown meatballs lightly on all sides, working in two batches, then remove them to a clean plate.

Melt butter in the same skillet you used for the meatballs, then add onion and cook for 2-3 minutes, until beginning to soften. Add crushed tomatoes, remaining 1/2 teaspoon Italian seasoning, and red pepper flakes, if using. Scrape the bottom of the pan to release any browned bits. Bring the mixture to a simmer and cook for 2-3 minutes. Remove from the heat and season with additional salt and pepper to taste.

Add the drained pasta to the sauce and stir well. Mix in about half of the mozzarella and the remaining 1/4 cup Parmesan. Spread into an even layer, then nestle the meatballs in among the pasta. Sprinkle remaining mozzarella on top.

Bake for 20-25 minutes, until the sauce is bubbling and the meatballs reach 165 degrees F inside. Top with additional breadcrumbs, if desired, and broil for 1-2 minutes, just until browned. Remove, garnish as desired with fresh parsley or basil, and serve.