Preheat the oven to 350°F (175°C). Grease a loaf pan or line it with parchment paper.
Sauté mushrooms and onions in a skillet over medium heat until soft. This removes excess moisture and enhances flavor.
Mix ingredients: In a large bowl, combine ground beef, pork, breadcrumbs, milk, Parmesan, sautéed mushrooms & onions, bacon, eggs, Worcestershire sauce, ketchup, garlic powder, thyme, salt, and pepper. Mix gently—do not overwork the meat.
Assemble the meatloaf: Place half of the meat mixture into the loaf pan and flatten. Sprinkle half of the shredded Swiss cheese on top. Add the remaining meat mixture, pressing it down firmly. Top with the rest of the Swiss cheese.
Bake for 55-60 minutes, or until the internal temperature reaches 160°F (71°C). For a crispy cheese crust, broil for the last 5 minutes.
Let the meatloaf rest for 10 minutes before slicing. This keeps it moist and allows flavors to meld.
Serve warm with mashed potatoes, roasted vegetables, or a fresh green salad.