Creating French Onion Meatballs is a straightforward process. Follow these steps to achieve the best results:

1. Preheat the Oven: Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
2. Mix Meatball Ingredients: In a large bowl, combine ground beef, breadcrumbs, grated Parmesan, chopped onion, minced garlic, egg, Worcestershire sauce, salt, pepper, and thyme. Mix until just combined.
3. Form Meatballs: Shape the mixture into meatballs about 1 to 1 1/2 inches in diameter. Place them on the prepared baking sheet, spacing them evenly.
4. Bake Meatballs: Bake the meatballs in the preheated oven for 20-25 minutes or until they are cooked through and browned.
5. Caramelize Onions: While the meatballs bake, heat a skillet over medium heat and add your caramelized onions. Stir occasionally until heated through.
6. Add Cheese: Once the meatballs are done, remove them from the oven and top each meatball with a spoonful of caramelized onions and a generous sprinkling of shredded Gruyère cheese.
7. Broil for Finish: Place the meatballs back in the oven under the broiler for 2-3 minutes until the cheese is bubbly and golden.