Preheat the oven to 425°F.
In a bowl, combine the chicken, panko, 1/3 cup parmesan, egg, and 1 tablespoon Italian seasoning. Season with salt and pepper, then mix until just combined. Coat your hands with olive oil and roll the mixture into meatballs, making 15–16 meatballs.
Arrange the meatballs in a baking dish. Bake for 15 minutes, until beginning to crisp on the outside.
Meanwhile, in a bowl, mix the heavy cream, 2/3 cup parmesan, and 1 tablespoon Italian seasoning. Season with salt and pepper.
Remove the baking dish from the oven. Add the butter, garlic, and chili flakes to the hot dish. Let the garlic sizzle in the butter for 2 minutes. Add the spinach, then pour the marinara and parmesan cream sauce over everything. Gently stir the sauces around the meatballs and top with torn mozzarella.
Return the dish to the oven and bake for another 15 minutes, until the meatballs are cooked through (165°F), the sauce is bubbling, and the cheese is melted.
Serve the meatballs and sauce over your favorite spaghetti. Top with fresh basil and enjoy!