Start by preheating your oven to 350°F (175°C). While it’s heating, line a baking sheet with parchment paper or lightly grease a loaf pan. If you're using a loaf pan, this helps keep the meatloaf together and ensures it cooks evenly.

In a skillet over medium heat, add a drizzle of olive oil and sauté the chopped onion for about 5-7 minutes until they become soft and caramelized. This step brings out their natural sweetness and adds richness to the meatloaf. Set them aside to cool for a minute before adding to your meat mixture.

In a large mixing bowl, combine the ground beef (or turkey), French onion soup mix, breadcrumbs, egg, Worcestershire sauce, garlic powder, salt, pepper, milk, and the sautéed onions. Use your hands (or a spoon) to gently mix everything together, making sure not to overwork the meat, which can make the meatloaf tough.

Transfer the meat mixture to your prepared baking sheet or loaf pan. Shape the meat into a loaf, pressing gently to ensure it's even. If you're using a baking sheet, form a rectangular loaf shape about 9 inches long and 5 inches wide. The evenness helps the meatloaf cook consistently.

Top your meatloaf with a generous layer of shredded mozzarella cheese. If you’re craving extra cheesy goodness, feel free to add more! Pop the meatloaf in the oven and bake for about 50-60 minutes, or until the meatloaf reaches an internal temperature of 160°F (71°C). Keep an eye on it, as oven times can vary slightly.

For an extra burst of French onion flavor, about 10 minutes before the meatloaf is done, pour a little French onion soup over the top. This adds moisture and creates a beautiful, savory glaze that will make every bite even more delicious.

Once your meatloaf is cooked, remove it from the oven and let it rest for 10 minutes. This helps it set, making slicing easier and ensuring you don’t lose all those juicy flavors. Slice it into thick portions, garnish with fresh parsley, and get ready to enjoy!