deglaze
Add liquid (wine, stock, water) to a hot pan after searing or browning, scraping up the browned bits stuck to the bottom -- these bits are called the fond, and they carry a lot of flavor. Fond is deep brown and smells savory; if what is stuck to the pan is black and smells acrid it has burnt, and scraping it in spreads that bitterness through the whole dish.
How to do it
After the browned food comes out of the pan, take a look at what's left behind -- you want deep golden-to-brown fond, not a layer of black, burnt material. Pour off excess fat if there's a lot, but leave the fond itself in place. Put the pan back over moderate heat and add the deglazing liquid, which should bubble rapidly right away. Scrape the bottom of the pan with a wooden spoon or similar utensil while the liquid works the fond loose, and keep cooking to reduce the liquid further if a more concentrated sauce is what you want.
Common pitfalls
- Trying to save genuinely burnt fond -- black, acrid residue will make the whole sauce taste bitter.
- Adding too much liquid -- it dilutes the flavor you're trying to capture.
- Not scraping thoroughly -- the best flavor is still stuck to the pan.
- Using a nonstick pan when the point is fond -- nonstick surfaces are built to minimize sticking, so less fond forms in the first place.
- Adding alcohol over an open flame carelessly -- the vapor it gives off can ignite.
Why it works
Browning generates a large family of flavor compounds, and much of that residue stays stuck to the pan rather than going anywhere. Adding liquid dissolves the water-soluble parts of it and physically loosens the browned particles, and continued boiling then removes water through evaporation, concentrating what's left into a proper sauce. Wine and other alcoholic liquids can carry some aromas a little differently than water alone, though most of what they contribute comes from their acidity, sugar, and fermentation-derived flavor rather than the alcohol itself.
Equipment
Stainless steel is arguably the classic pan for deglazing, since it develops visible fond readily. Use a wooden spoon, silicone spatula, or whisk depending on what the finished sauce needs. The pan should have enough surface area that the liquid can reduce efficiently once it's in there.