Prepare the mixture: In a large bowl, combine the ground beef, Parmesan cheese, salt, chili flakes, parsley, pepper, thyme, garlic, and egg. Mix well with your hands until fully integrated.
Form the meatballs: Use a #20 scoop to make evenly sized meatballs and shape them with your hands.
First bake: Place the meatballs in an oven-safe dish and bake at 390F for 15 minutes.
Flip and continue baking: Turn the meatballs over and bake for another 10 minutes until golden.
Add sauce and cheese: Remove the dish from the oven, cover the meatballs with marinara sauce, and sprinkle with mozzarella cheese.
Final bake: Return to the oven for 10 more minutes, or until the cheese melts and turns golden brown.
Garnish with fresh parsley or basil leaves. Serve hot, with mashed potatoes or pasta if desired.