1. Heat a large skillet over medium heat and add the ground beef and chopped onion. Cook until the beef is browned and the onion is soft, then drain any excess grease.

2. Stir in the garlic, taco seasoning, salsa, salt, and black pepper. Cook for 2 to 3 minutes until the mixture is well combined and slightly thickened.

3. Lay the tortillas on a flat surface. Sprinkle cheddar and mozzarella over one half of each tortilla.

4. Spoon the beef mixture evenly over the cheese, then top with a little more cheese. Fold each tortilla in half.

5. Wipe out the skillet and return it to medium heat. Add a little butter or oil. Cook the quesadillas in batches for 2 to 3 minutes per side until golden brown and crisp and the cheese is melted.

6. Transfer to a cutting board, rest for 1 minute, then slice into wedges.

7. Garnish with parsley or cilantro and serve warm.