1Lightly grease the crockpot or line it with parchment paper.
2In a large bowl mix ground beef, breadcrumbs, egg, milk, diced onion, French onion soup mix, black pepper, paprika, and Worcestershire sauce until combined.
3Shape the mixture into a loaf and place it in the crockpot.
4Pour the canned French onion soup around the meatloaf.
5Cover and cook on LOW for 6–7 hours or HIGH for 3–4 hours until the meatloaf is fully cooked.
6During the last 10–15 minutes, place Swiss cheese slices over the meatloaf.
7Cover again and allow the cheese to melt.
8Carefully remove the meatloaf, spoon some onion gravy over the top, garnish with parsley, and serve warm.