Pasta cooking water
“The cooking water from pasta is a culinary gem,” says Retelny. “It contains the natural starch from the pasta—and depending on the type of pasta, it can contain vitamins and minerals too. This liquid can be immediately added to thicken and flavor pasta sauces. Or freeze it into ice cube trays and throw a cube into stocks or broths, soup, and chili, or gravies and sauces.”