Those potato swirls definitely add an extra layer of amazingness to this dinnertime meal recipe. We use a Wilton 6B open flower cake tip for those swirls. But really, any large tip will make a beautiful design. We also use the Wilton plastic cake decorating and pastry bags to make it even easier for this recipe. These disposable bags make for the easiest and fastest clean up... for cakes or the potato swirls. However, the swirls aren't absolutely necessary. We've eaten this dish plenty of times with the mashed potatoes spread evenly over the meat mixture using an angled spatula. This spatula helps evenly spread the potatoes into the corners and sides of the dish. You could also just use the back of a spoon or wooden spoon to spread the potatoes evenly over the beef mixture.