Reduction is simply the act of evaporating water to concentrate flavor and thicken texture. Water boils at 212°F, and as it escapes as steam, it leaves behind all the good stuff: sugars, salts, and glutamates. This is why a demi-glace tastes like liquid gold—it’s just stock that has said goodbye to half its volume.
The trick is patience. You cannot bully a sauce into submission; you must nurture it with steady, gentle heat. Crank the burner to high, and you’ll risk scorching the bottom, creating bitter notes that no amount of butter can fix. Aim for a lively simmer—those lazy, dancing bubbles that whisper, not scream.
