To serve, cook pasta according to package instructions in a
large pot of salted boiling water until very al dente (perhaps more al dente than usual). Transfer to
Dutch oven with remaining shallot mixture (or a
skillet if you are using the leftover portion) and 1 cup pasta water. Cook over medium-high heat, swirling the
skillet to coat each piece of pasta, using a wooden spoon or
spatula to scrape up any bits on the bottom, until pasta is thick and sauce has reduced and is sticky, but not saucy, 3 to 5 minutes.