Preheat the oven to 350°F. Spray a 13 x 9 inch baking dish with cooking spray. Set aside.
In a large pot cover the 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.
Add the melted butter, light cream, sour cream, garlic salt, black pepper, granulated garlic, onion powder and paprika. Mix well.
Fold in 2 cups shredded white cheddar cheese and sliced green onions. Reserve some green onion for garnishing.
Pour the mixture into the dish. Top with the remaining shredded cheese and sprinkle with a light dusting of paprika.
Bake for 35-40 minutes. Garnish with reserved chopped green onion just before serving.