Step 1: Prepare the Meatloaf Mixture

1. Combine the Ingredients:
   In a large mixing bowl, combine the ground beef, breadcrumbs, grated Parmesan cheese, milk, eggs, Worcestershire sauce, salt, and black pepper. Use your hands or a spoon to gently mix the ingredients until they are just combined. Be careful not to overmix, as this can make the meatloaf tough.
2. Shape the Meatloaf:
   Once the ingredients are well combined, shape the mixture into a loaf. Place the loaf in the bottom of your crockpot, ensuring that it is centered and not touching the sides.

Step 2: Prepare the French Onion Topping

3. Caramelize the Onions:
   In a large skillet, melt the butter over medium heat. Add the thinly sliced onions and cook, stirring occasionally, until they are caramelized and golden brown, about 15 minutes. The caramelization process is key to developing the deep, sweet flavor of the onions, so take your time with this step.
4. Add the Onions to the Crockpot:
   Once the onions are caramelized, carefully pour them over the top of the meatloaf in the crockpot. Pour the beef broth over the onions and meatloaf, ensuring that the broth covers the bottom of the crockpot.

Step 3: Cook the Meatloaf

5. Slow Cook:
   Cover the crockpot with the lid and cook the meatloaf on low for 6-7 hours, or until the meatloaf is fully cooked and tender. The slow cooking process allows the flavors to meld together, resulting in a juicy, flavorful meatloaf.

Step 4: Add the Swiss Cheese

6. Top with Cheese:
   About 15 minutes before you’re ready to serve, remove the lid from the crockpot and carefully place the slices of Swiss cheese over the top of the meatloaf. Cover the crockpot again and allow the cheese to melt over the meatloaf.

Step 5: Serve and Enjoy

7. Serve:
   Once the cheese is melted, carefully lift the meatloaf out of the crockpot using a spatula and place it on a serving platter. Slice the meatloaf into portions and spoon the caramelized onions and broth over each slice.