Place potatoes in a large pot. Cover with water and bring to a boil. Reduce heat; cover and cook for 15-20 minutes, or until potatoes are tender. Drain really well, making sure that the potatoes are dry. Transfer the potatoes to a large bowl. Add cream cheese, cheddar cheese, sour cream, milk, 2 tablespoons of the melted butter, garlic salt, and chives.
Beat the potatoes until well blended and fluffy. Taste and season with salt and pepper, as necessary. Transfer the potatoes to a 3-quart baking dish that has been sprayed with cooking spray.
In a small bowl, toss together Corn Flakes crumbs and remaining 1 tablespoon of melted butter. Sprinkle over top of the potatoes.
Bake, uncovered, at 350°F for 30-35 minutes, or until the edges are bubbly and the potatoes are heated through. Sprinkle paprika over top, garnish with chives, parsley, or green onions if desired, and serve!