Add the ground beef to the skillet with the onions, Italian Seasoning, ground mustard, garlic powder, salt and pepper to taste. Cook until done.
Add the cooked beef along with the diced potatoes, broth, and Worcestershire sauce to the slow cooker.
Cook on High for 3-4 hours or on Low for 7-8 hours.
Open the pot and add the half and half, shredded cheddar, and cream cheese. Stir and cook on High for 15-20 minutes until the soup thickens and the cheese melts.
Create a slurry using 1 tablespoon of all-purpose flour and 1 tablespoon of water. Combine in a bowl with 1 tablespoon of cooked soup. Stir and add the mixture to the pot.