Cook cubed potatoes until tender. Preheat over to 350°. In food processor, puree potatoes, milk, black pepper and basil. Drain and flake tuna. Add to bowl along with scallions and 1 1/2 cups cheese. Pulse on and off until mixture is thoroughly blended. Place root vegetables in 8x8 in baking dish. Spread potato-tuna mixture (brandade) over root vegetables. Sprinkle with cheese.** Bake 20 minutes or until heated through and browned on top.
any left over vegetables that are still firm. Note:**dish may be prepared up to this point and refrigerated. When ready to proceed bring dish to room temperature and bake as above.