If you've been pouring your pasta water down the drain, you're guilty of culinary crime. Not felony-level, granted, but it's a bad habit that needs correcting, pronto. The water in which you boil your pasta is a convenient by-product that makes your pasta dish more delicious, binding the sauce to the pasta, while also improving the flavor and texture of the sauce. Here's how to get the most out of it.
First, nevermind what you've been told since the very first time you boiled pasta: It does not need to cook in gallons and gallons of water. The magic of pasta water derives from the starch the pasta releases as it cooks. Using a lot of water means diluting the pasta liquid, rendering it practically useless.
This will sound like heresy, but it's actually becoming accepted practice among chefs and savvy home cooks alike: Only use as much water as you need to cover the pasta as it boils. The noodles will not stick together, as long as you give them a few good stirs during the first two minutes of cook time. And when the pasta is done, the starch content will be wonderfully concentrated in pasta water that's noticeably viscous.
You'll ladle a few tablespoons of it into the pasta as it finishes cooking with the sauce in a separate pan, which helps the sauce adhere to the noodles and gives the sauce itself a gloriously silky texture.
So far, so good. But when you dump the remaining pasta water down the drain, that's where you make the pasta gods cry. Treat it like stock, and freeze it in small batches (ice cube trays are perfect for this), and add a cube or two to future soups and stews, risotto, or even adjust the consistency of gravy.