Preheat the oven to 350°F. Grease a 9x13 inch baking dish. Set aside.
In a large bowl, combine the thawed hash brown potatoes and diced ham. Set aside.
In a separate bowl, whisk together the cream of chicken soup, sour cream, milk, Dijon mustard, dried thyme, onion powder, garlic powder, salt, and black pepper until well-combined.
Pour the soup mixture over the hash brown and ham mixture.
Add 1 cup of the shredded cheddar cheese and mix well to combine.
Transfer the mixture to the prepared baking dish, spreading it out in an even layer.
Cover the casserole with aluminum foil, and bake for 35 minutes.
Remove the foil and sprinkle the remaining 1 cup of shredded cheddar cheese evenly over the top of the casserole.
Return the casserole to the oven and bake for an additional 10-12 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let the casserole sit for 10-15 minutes before serving. This resting time helps the casserole to set.
Notes
Ham: Cut up a whole ham into bite-sized chunks. Or use pre-packaged ham chunks instead of diced ham.
Cheese: Substitute with other cheeses like triple cheddar cheese blend or Monterrey Jack cheese.
Cream of chicken soup: Use cream of mushroom or cream of celery soup for different flavor. You can also make your own cream of chicken substitute with this recipe.
Milk: You can use any milk from skim milk to whole milk.