To a 6-quart slow cooker, add the frozen hash brown potatoes, onion, chicken broth, ham, garlic powder, thyme, and pepper. Stir everything together.
Cover and cook on LOW for 8 hours without opening the lid during the cooking time.
When the cooking time is up, add the cream cheese to a blender, and scoop a ladleful of broth and hot potatoes into the blender with the cream cheese. (You just need enough soup to get the blender moving.) Cover and blend until smooth.
Pour the cream cheese mixture back into the rest of the soup still in the slow cooker. Add the shredded cheddar and stir until melted.
Check the seasoning and add salt and pepper to taste as needed. Serve warm with bread and butter.
Notes
Don't buy pre-shredded cheese for this recipe! It won't melt as well as block cheese shredded at home.