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Preheat oven to 400°F.
In a large, oven-safe skillet, heat olive oil over medium high-heat. Add onion, half of the garlic and season with salt and pepper. Sauté for 3-4 minutes then add tomato paste and cook for another minute. Deglaze with red wine and reduce by half. Add tomatoes and bring the sauce to a bubble. Reduce heat to a simmer and cook for 8-10 minutes.
In a food processor, pulse rolled oats for a few seconds until they are finely ground but not powdery.
In a mixing bowl, completely combine ground oats and milk. Add chicken, egg, egg white, remaining garlic, cheese, spinach, chili flakes, oregano, salt and pepper. Using your hands, combine mixture well, making sure not to overmix.
Using a 2- to 3-inch kitchen scoop, scoop and place meat on a plastic cutting board or plate. Place a cube of mozzarella cheese into each meatball and roll or fold the meat around the cheese. Nestle the meatballs into the skillet with the sauce so they are covered at least halfway. Place the skillet in the oven until sauce is bubbly and thick, and the meatballs are cooked through, about 20-25 minutes. Remove from oven and garnish with basil.
Serve over spaghetti or zoodles.