Combine cooked chicken, butter, buffalo sauce, and water in the instant pot. Place the lid on and the valve to seal and cook on high pressure for 3 minutes. Do a quick release.
4 Cups Chicken, 3/4 Cup Buffalo Sauce, 2 Tablespoons Butter, 1/4 Cup Water
Stir in the ranch dressing, cream cheese and 1 cup of shredded cheddar cheese. Place lid on and wait 5 minutes then stir again.
Pour out into a casserole dish. Turn the oven to 400 degrees. Sprinkle the remaining shredded cheddar cheese over the top and bake until cheese is melted. Serve with chips, crackers, or veggies.