The cloudy liquid left in the pot after cooking pasta is one of the most overlooked ingredients in Italian cooking, yet many home cooks pour it straight down the drain. As pasta boils, it releases starch into the water, creating a lightly thickened liquid that acts as a natural emulsifier. When added to a cheese-based sauce like cacio e pepe, that starch helps bind fat and liquid together smoothly, preventing the sauce from splitting or becoming greasy. Marcus Wareing pointed out that Anthony made a critical error by not using pasta water, relying on butter alone to bind the cheese. Always reserve at least one generous ladle of pasta water before draining — just in case.