Boil potatoes in salted water. Drain and mash with butter, bouillon, garlic, Italian seasoning, and salt. I use my food processor to get them nice and smooth. You want to make sure you don't add liquid unless it's necessary to mash them, otherwise your pie won't cut very nicely. Set aside.
Preheat oven to 350 degrees F. Combine uncooked beef, bread crumbs, onion, salt, garlic powder, egg and 3 tbsp BBQ sauce. Press into ungreased 9" pie plate or 9" square baking dish and up the sides to form the crust. Brush meatloaf with remaining 3 tbsp BBQ sauce.
FIll with mashed potatoes.Sprinkle with shredded cheese. (*Note: I find low fat cheese gets dried out if in the oven for long periods of time. If using low fat cheese, you may want to leave it off until near the end. You may want to cover your potatoes with a greased sheet of tin foil to keep them from drying out).
Bake at 350 degrees F for 45 minutes. Sprinkle with tomatoes, bacon and green onions (or any other toppings you want!).