Heat a large skillet over medium heat. Add olive oil and ground beef. Cook until browned and fully cooked, breaking it into small pieces for a soft, crumbly texture.

Add chopped onion to the pan with cooked beef. Cook for about 3 to 4 minutes until soft. Stir in garlic and cook briefly until fragrant and lightly golden.

Add tomato sauce and tomato paste to the skillet. Stir well until combined. The mixture will become rich and thick, forming a flavorful base for the dish.

Sprinkle oregano, basil, red pepper flakes, salt, pepper, and sugar into the mixture. Stir well to combine and let the flavors blend together evenly in the sauce.

Reduce the heat to low and let the mixture simmer for about 8 to 10 minutes. Stir occasionally so the sauce thickens and develops a rich, balanced flavor.

Add shredded mozzarella cheese into the pan. Stir until it melts completely and blends into the sauce, creating a creamy and rich Italian-style sloppy joe filling.

Lightly toast the hamburger buns in a pan or oven until slightly crisp. This helps them hold the filling better and prevents them from becoming soggy when served.

Spoon the hot sloppy joe mixture onto the bottom half of each bun. Add extra cheese if desired, then place the top bun over the filling and press gently.

Sprinkle fresh parsley on top for a bright finish. Serve immediately while warm so the filling stays juicy and the buns remain slightly crisp and delicious.