Preheat the oven to 350°F. Spray a 13 x 9 inch baking dish with cooking spray.
In a large pot cover the cubed potatoes with water. Season the water with with 1 tsp salt. Bring to a boil cooking for 12-15 minutes until fork tender. Drain well.
Add to a large mixing bowl and using a potato masher roughly smash the potatoes leaving chunky.
In a separate bowl, whisk together half & half, onion soup, sour cream, melted butter, dry salad dressing mix, garlic salt, black pepper and paprika. Use a large spoon or spatula mixing until combined.
Add the sauce to the potatoes along with 2 cups shredded cheese, chopped chicken, crumbled bacon and green onion. Reserve some bacon crumbles and green onion for garnishing.
Pour the mixture into the dish. Top with the remaining 1 cup shredded cheese and sprinkle with a light dusting of paprika. Dot with 2 Tbsp cubed butter.
Bake for 40-45 minutes or until golden and bubbly. Garnish with reserved bacon and green onion just before serving