Preheat your oven to 350°F (175°C) to ensure it is hot and ready for cooking.
In a medium skillet, heat the olive oil over medium heat. Once the oil is shimmering, add the finely diced onion. Sauté for 10-12 minutes, or until the onion becomes soft and golden brown. Stir in the minced garlic and cook for an additional 1-2 minutes, until fragrant. Remove the skillet from heat and allow the onion and garlic mixture to cool slightly.
In a large mixing bowl, combine the ground beef and ground turkey, ensuring they are well mixed.
Add the cooled caramelized onion and garlic mixture to the meat mixture.
Add the breadcrumbs, grated Parmesan cheese, eggs, Worcestershire sauce, balsamic vinegar, dried thyme, salt, and black pepper to the bowl. Gently stir the mixture until all the ingredients are just combined, being careful not to overwork the meat.
Shape the mixture into a loaf and carefully transfer it to a baking dish, ensuring it holds its form.
Pour the beef broth around the meatloaf in the baking pan.
Place the meatloaf in the preheated oven and bake for approximately 1 hour, or until the internal temperature reaches 160°F (70°C).
After baking, remove the meatloaf from the oven and allow it to rest for about 10 minutes.
Before serving, garnish the meatloaf slices with freshly chopped parsley.
Notes
Serve with creamy mashed potatoes and green beans for a complete meal.