When thinly sliced fennel is thoroughly caramelized, it goes from a crisp, peppery, raw salad element to a delightfully decadent pasta sauce base. Those anise-y, licorice notes mellow as the natural sugars in the fennel caramelize. This recipe calls for pasta to be boiled until al dente (slightly undercooked) in salted water, then cooked a few minutes more with the caramelized fennel for perfectly tender pasta. To preserve most of those caramelized bits stuck to the bottom of the pot, it also calls for splashes of white wine, which capture and release them, and add pleasant acidity to the sauce. To complete the dish, the pasta, caramelized fennel and freshly chopped fennel fronds are showered with Parmesan and tossed until coated and the sauce becomes silky and glossy.