The best way to keep it from sticking and ready for saucing is to not cook the pasta until the sauce is ready for it. Period. Marcella Hazan, renowned author of many cookbooks on Italian cooking, says unequivocally, “Have the sauce ready when the pasta is done. Do not let drained pasta sit in the colander waiting for the sauce to be finished or reheated; once the pasta is sauced, serve it promptly, inviting your guests and family to put off talking and start eating. The point to remember is that from the moment the pasta is done, there should be no pauses in the sequence of draining, saucing, serving, and eating.”
In an ideal world, this is how it should work all the time. But one’s timing isn’t always perfect, and real life intervenes. So if you realize the pasta will be ready before the sauce, what can you do? There are a couple of things. If it’s not going to be long, say a couple of minutes, finish cooking the pasta and drain it in a colander, reserving a half cup of the cooking water. If the sauce is dairy-based, toss the pasta in a warm bowl with a couple of tablespoons of butter. If the sauce is oil-based, use olive oil. Add the sauce when it’s ready, toss the pasta and sauce together thoroughly (including any cheese if it’s called for, so it can melt), and add a little of the cooking water if needed to loosen the texture of the sauce. Rather than toss in a serving bowl, combine the pasta and sauce in a still-warm pan – the saucepan if it’s large enough; the pasta pot if it’s not. The residual heat will keep things from cooling off too fast. Serve immediately.
So how is it done in restaurants and other food service establishments where the kitchen doesn’t have the time to cook every pasta dish to order? They parboil the pasta in large quantities, cool it, and finish the heating and saucing of individual orders as needed. Note the word “parboil,” which means the pasta isn’t completely cooked first. It should be slightly undercooked so it’s not overdone when reheated. For most pastas, drain about a minute before it’s the desired degree of al dente. You’ll want to be especially careful if using a thin pasta like linguine or spaghetti, because those shapes can overcook more quickly.
To cool pasta, rinse it well with cold water and drain thoroughly. It can also be spread out in a thin layer on a sheet pan and refrigerated if you have the space in your refrigerator. When it’s cooled this way, you can toss the parboiled pasta with a little olive oil to keep it from sticking together. It doesn’t matter is the sauce is dairy-based, because the oil will dissolve into the cooking water when the pasta’s reheated.
To finish cooking, bring more salted water to a boil; you won’t need as much as for the initial cooking. Add the parboiled pasta in a basket, steamer basket, or china cap to make it easier to remove, or just drop it in. Let it simmer long enough to heat through and finish cooking; the time will depend on the thickness of the pasta. Remove from the water and drain well before continuing with the recipe. (If you’ve ever wondered why there’s a piece of spaghetti in with your order of rigatoni, now you know how that came about.)