Talk about comfort food, stop you're here! I use this recipe a lot, especially when I'm expecting guests for dinner. I make my own pasta, usually in the afternoon of the day my guests are expected. Locatelli is a delicious cheese, but if you're having trouble finding it, just go with a piece of Parmesan that you can create curls with. I also interchange the arugula with spinach. Both are fine. As for the pappardell, it is a wide pasta, looks sort of like lasagna, but don't use that it's too thick. If you don't make your own Pappardelle, and can't find it in your stores, just go with a wide noodle shape. It's so good, any shape is going to be great. Just improvise!