Preheat oven to 350 degrees.
Whisk together the melted butter, nacho cheese soup, sour cream, taco seasoning, salt and half of the cheddar cheese.
Add the frozen, cubed potatoes and the shredded white chicken to a large bowl. Add the nacho cheese soup mixture to the potatoes and chicken and mix until well-combined.
Spray a 9x13 casserole dish with cooking spray. Evenly spread the potato and chicken mixture into the casserole dish.
Top the casserole with the remaining shredded cheddar cheese.
Bake at 350 degrees for 1 hour.
Serve the casserole immediately, topped with fresh salsa.