01 -
In a large mixing bowl, combine ground beef, breadcrumbs, grated Parmesan cheese, whole milk, eggs, Worcestershire sauce, kosher salt, and ground black pepper. Blend thoroughly by hand until the mixture is uniform.
02 -
Shape the mixture into a cohesive loaf and set it in the base of the crockpot.
03 -
In a large skillet over medium heat, melt unsalted butter and add sliced onions. Cook, stirring regularly, for about 20 minutes until onions are deeply golden and softened.
04 -
Pour beef broth into the skillet with caramelized onions and simmer until the liquid is absorbed and the mixture is glossy.
05 -
Distribute the caramelized onion mixture evenly across the top of the uncooked meatloaf in the crockpot.
06 -
Cover and cook on low for 6 to 8 hours until the meatloaf reaches a safe internal temperature and is set.
07 -
Ten minutes before serving, layer Swiss cheese slices over the top. Allow to melt under the closed lid.
08 -
Gently lift the meatloaf out of the crockpot, slice, and serve each portion topped with melted Swiss cheese and caramelized onions.