In a large mixing bowl, gently combine the ground beef, Parmesan cheese, salt, chili flakes (if you like a little kick!), fresh parsley, black pepper, dried thyme, minced garlic, and the egg. Use your hands to mix until all ingredients are just incorporated, being careful not to overmix to keep the meatballs tender.
Scoop out about 2 tablespoons of the mixture for each meatball and gently roll them into uniform, round shapes. You should get approximately 15 meatballs from this recipe.
Arrange your perfectly shaped meatballs in a single layer in an oven-safe baking dish. Bake in a preheated oven at 390°F (199°C) for 15 minutes to start the cooking process.
Carefully turn each meatball over to the other side. Return the dish to the oven and continue baking for another 10 minutes, allowing them to develop a nice golden-brown crust.
Remove the dish from the oven. Evenly pour your chosen marinara sauce over all the meatballs, then generously sprinkle the shredded mozzarella cheese on top.
Place the dish back into the oven for a final 10 minutes, or until the mozzarella cheese is beautifully melted, bubbly, and slightly golden brown.
Garnish your delicious meatballs with a sprinkle of fresh parsley or basil leaves for extra aroma and flavor. Serve hot as a healthy, satisfying meal, perhaps alongside a simple salad or steamed vegetables.