FIRST STEP: PREPARE THE MEATLOAF MIXTURE

1. Sauté the Onions and Garlic: In a skillet, heat 1 tablespoon of olive oil over medium heat. Add the chopped onion and cook, stirring occasionally, until it turns soft and golden, about 6-8 minutes. Add the minced garlic and cook for another 1-2 minutes until fragrant. Set aside to cool.
2. Combine the Meatloaf Ingredients: In a large mixing bowl, add the ground beef, breadcrumbs, milk, thyme, salt, pepper, and the cooled sautéed onion and garlic mixture. Use your hands or a spatula to gently combine everything, ensuring the ingredients are well-mixed but not overworked.
3. Add the Egg: Crack the egg into the mixture and stir until it’s fully incorporated. The egg helps bind the ingredients together and provides structure to the meatloaf.
4. Shape the Meatloaf: Transfer the meat mixture into a 9×5-inch loaf pan. Use your hands to press the meat into an even, compact shape. If you prefer a crisper crust on all sides, you can shape the meat into a loaf on a baking sheet instead of using a loaf pan.

SECOND STEP: CARAMELIZE THE ONIONS FOR THE TOPPING

1. Heat the Butter and Olive Oil: In a large skillet, heat the butter and olive oil over medium heat. Add the thinly sliced onions and stir to coat in the butter and oil.
2. Cook the Onions: Reduce the heat to low and cook the onions slowly, stirring occasionally, until they become soft, golden brown, and caramelized, about 25-30 minutes. Be patient—this process helps develop the sweet, rich flavor of the onions.
3. Add Beef Broth and Worcestershire Sauce: Once the onions are caramelized, pour in the beef broth and Worcestershire sauce. Stir to combine, allowing the broth to cook down slightly and the mixture to thicken. Let this simmer for another 5-10 minutes, then remove from the heat.

THIRD STEP: ASSEMBLE AND BAKE THE MEATLOAF

1. Top the Meatloaf with Onions: Spoon the caramelized onion mixture evenly over the top of the prepared meatloaf. Spread it out to cover the entire surface.
2. Add Cheese: Sprinkle the shredded Gruyère or Swiss cheese generously over the onions. The cheese will melt and form a golden, bubbly crust on top of the meatloaf.
3. Bake: Preheat the oven to 350°F (175°C). Place the meatloaf in the oven and bake for about 60 minutes, or until the meatloaf is fully cooked through (the internal temperature should reach 160°F or 71°C). The cheese on top should be melted and lightly browned.
4. Rest the Meatloaf: Once the meatloaf is cooked, remove it from the oven and let it rest for about 10 minutes before slicing. This helps the juices redistribute and makes for easier slicing.

FINAL STEP: GARNISH AND SERVE

1. Garnish: Before serving, sprinkle freshly chopped parsley on top of the meatloaf for a burst of color and freshness.
2. Slice and Serve: Slice the meatloaf into 6-8 servings, depending on your preferred portion size. Serve hot with your favorite side dishes, such as mashed potatoes, roasted vegetables, or a fresh salad.