The secret ingredient to an amazing, restaurant-worthy pasta recipe like this one is shockingly simple. Its just water Pasta water, that is. Using just cup of the leftover penne cooking liquid adds starchy body to the pan sauce, which helps the flavors to emulsify into a rich coating thats full of flavor and body. The liquid pulls the salty pan drippings from the prosciutto and the garlicky oil and slicks it onto each tube of pasta. Thats why penne is great for a dish like this onethe ridges encourage sauce to stick and the tube traps delicious pockets of sauce. And by the way, this simple pasta water technique is the kind of back-pocket trick that you can pull out with any pasta dish.