Step 1: Preheat your oven to 375°F (190°C).
Step 2: In a large bowl, combine the ground beef, breadcrumbs, milk, egg, 1/4 cup chopped onion, minced garlic, Worcestershire sauce, salt, and pepper. Mix gently until just combined; do not overmix.
Step 3: For the stuffing, heat olive oil in a skillet over medium heat. Add the finely chopped mushrooms and cook until softened and all liquid has evaporated, about 5-7 minutes. Stir in the remaining 1/4 cup chopped onion and cook for another 2-3 minutes until softened. Remove from heat and let cool slightly.
Step 4: Once cooled, mix the shredded Swiss cheese into the mushroom mixture.
Step 5: On a large piece of parchment paper or a clean cutting board, press the meatloaf mixture into a rectangle, about 10x12 inches and 1/2-inch thick.
Step 6: Spoon the mushroom and Swiss cheese stuffing down the center of the meatloaf rectangle, leaving a border around the edges.
Step 7: Carefully lift one long side of the parchment paper to help roll the meatloaf tightly, enclosing the stuffing. Pinch the ends and seams to seal the loaf.
Step 8: Arrange the bacon slices over the top of the meatloaf, overlapping slightly, to form a complete crust. Tuck the ends of the bacon underneath the meatloaf.
Step 9: Carefully transfer the bacon-wrapped meatloaf to a baking dish or a foil-lined baking sheet.
Step 10: Bake for 1 hour 15 minutes, or until the internal temperature reaches 160°F (71°C). If bacon is not crispy enough, you can broil for the last few minutes, watching carefully to prevent burning.
Step 11: Remove from oven and let the meatloaf rest for 10-15 minutes before slicing and serving. This allows the juices to redistribute, ensuring a moist and flavorful result.