Place chicken, oat flour, basil, thyme, oregano, garlic, egg yolk, salt and pepper into a large mixing bowl and mix together until all ingredients are fully combined, making sure not to over-mix and toughen the meatball mixture.
Taking 2 tablespoons of the mixture at a time, flatten into a disc on the palm of your hand and place a cube of mozzarella onto the center of the disc. Mold the mixture around the cheese, into a ball and roll until completely sealed.
Combine all the ingredients of the dredging mixture together into a shallow baking dish and whisk together.
Lightly coat each meatball with the flour mixture, shaking off any excess. Continue by rolling each meatball into the beaten eggs and back into the flour mixture. Repeat this step until all meatballs have been coated.
Fill a skillet with 1 inch of oil and place over medium heat. Once the oil reaches 350˚F, carefully add a few meatballs to the skillet and fry for about 4 minutes on each side or until the meats are golden brown and just cooked through. Transfer onto paper towels and lightly season with salt and pepper.
Repeat until all meatballs have been fried. Garnish with fried basil leaves and grated Parmesan, if desired. Serve immediately with marinara sauce.