Preheat oven to 350. Coat a 9 x 13 inch baking dish with cooking spray.
Cook bacon in saute pan over medium heat til crisp. Transfer to a paper towel lined plate. Drain all but 1 Tbsp. drippings from pan. Add scallion whites and sweat til softened, about 1 minute; transfer to a large bowl.
Whisk in dip, Cheddar, milk, scallion greens, and cream cheese. Stir in hash browns and bacon; season with salt and pepper. Transfer mixture to prepared baking dish. Mix corn flakes and butter, season with salt and pepper and sprinkle over casserole. Bake casserole til golden and bubbly, about 45 minutes.