In a large skillet, or deep stock pot, melt 1/2 cup butter over medium heat. Add 1 can cream of chicken soup and the whipped cream cheese with chives. Stir until well blended.
Add in 1 cup cubed mild cheddar cheese, or shredded cheese, and 1/4 cup of milk. Continue stirring until cheese is melted and mixture is creamy.
Place a bag of frozen hash browns into a large bowl. Add cheese sauce mixture. Stir together.
Pour cheesy hash browns into a sprayed 2-quart baking dish, or 9 x 13 pan or casserole slow cooker.
Top with 1 cup of grated mild cheddar cheese and chopped fresh chives (optional).
If using the 2-quart baking dish, or 9 x 13 baking dish, bake in a preheated 350° F oven for 1 hour until fork tender.
If making in a casserole crock pot, bake on low for 3.5 hours or on high for 2 hours.