The pectoralis major, one on each side of the keel bone. There's no fat to melt and no collagen to turn to gelatin, so the only thing you control is how much water the muscle keeps. That makes it the least forgiving cut on the bird and the one where a thermometer matters most.
The breast sits high on the sternum and is the muscle a chicken uses to flap — a few seconds of hard work to clear a fence, then it's done. That's fast-twitch glycolytic muscle: it runs on stored glycogen rather than oxygen, so it carries very little myoglobin, which is why it's white, and it stores almost no fat inside the fibers. It also does no postural work, so there's barely any connective tissue in it — no seams worth speaking of, one grain running head to tail, and a separate strip underneath (the pectoralis minor, sold as the tender). Modern broiler breasts are much larger than they were a few decades ago: 8-12 oz each, 1.5 to 2 inches thick at the wide end and tapering under half an inch at the point. That wedge shape, not the cook's attention span, is what causes most dry chicken.
With no fat and no collagen, the entire outcome is water retention. Myosin denatures around 120-140F, which is when the meat firms up and goes opaque; actin denatures around 150-163F, and when actin goes the fiber contracts hard and wrings water out. That's the cliff, and it's one-way. A breast taken to 150F loses on the order of 12-15% of its weight; taken to 170F it loses 20-25%, roughly an extra ounce per breast, and that water is on the pan, not in the meat. Pasteurization is time at a temperature rather than one number: a 7-log Salmonella reduction takes an instant at 165F, about 45 seconds at 155F, about 3 minutes at 150F, and roughly 9 minutes at 145F. Holding a breast at 150-155F for a minute or two is as safe as hitting 165F and keeps the water.
The wedge is the problem, so remove the wedge — a uniform slab reaches its target everywhere at once instead of overcooking the thin end while you wait on the thick one.
HowButterfly it or pound it between two sheets of plastic to an even half inch, dry the surface, salt it, then 2-3 minutes per side in a pan around 400F. Pull at 150F.
Salt dissolves myofibrillar proteins so they hold more water under heat, and a gentle oven narrows the gap between surface and center so less of the outside overshoots.
HowSalt at 0.75-1% of the meat's weight (about 1 tsp Diamond kosher per pound), uncovered in the fridge 4-24 hours, no rinse. 275-300F oven to 145F internal — 20-30 minutes for a 10 oz breast — then 60-90 seconds a side in a hot pan. Final 150-155F.
Water held below the top of actin's denaturation range cannot push the meat past that range no matter how long it sits, so the doneness stops being a timing problem.
HowHold the water at 150-155F with a thermometer and low heat, 45-60 minutes for whole breasts. Sear afterward if you want color, or shred straight out of the pot.
The rib bones slow heat into the underside and the skin shields and bastes the top, so the same muscle cooks more evenly than it does naked.
How425F, skin up, 30-35 minutes for a 12-14 oz split breast, pulled at 155F at the thickest point clear of the bone. Rest 8-10 minutes.
The breast is a wedge, so over a 600F fire the thin end sails past 165F before the thick end reaches 140F, and the outer quarter inch of the entire piece runs past 180F and turns to chalk. The damage is water expelled by denatured actin, and it is permanent — a contracted muscle fiber does not reabsorb the liquid it squeezed out. Sauce, gravy, resting, and slicing thin all operate on the surface; none of them put water back inside the meat, they just make the dryness easier to swallow. The same unrecoverable mistake in another costume is boiling breast for shredded chicken: 212F water drives the interior well past 175F, and what you pull out is dry threads that only seem moist because they're sitting in liquid. If you want shredded breast, hold the water at 150-155F instead and it will pull apart just as easily.
Boneless skinless breasts commonly run 8-12 oz, which is too big to cook evenly — buy them and butterfly, or ask for split breasts (bone-in, skin-on), which are the same muscle left on the ribs and cook far more forgivingly. Air-chilled birds carry less added water and brown better. Look hard at the surface: meat that feels firm and ridged, with pale stripes of fat running with the grain, is woody breast and white striping, growth-related defects in fast-grown broilers where fibrous tissue has replaced muscle. That meat stays chewy no matter how it's cooked, and no technique fixes it. Check for 'contains up to X% solution' on the label — that's injected brine, and it steams before it sears.
Doneness: Pull at 150-155F and let it coast 3-5F. 145F is safe if it's held there about 9 minutes, which a water bath can do and a hot pan cannot. 165F is instantly safe and costs roughly 10% of the weight in water.
Because it went past about 160F. Breast has almost no intramuscular fat and almost no collagen, so there's nothing to compensate when actin denatures and the fibers squeeze water out. Cook to 150-155F and check with an instant-read at the thickest point, not by time or by cutting into it. If it's still coming out dry at that temperature, the piece is uneven — butterfly it flat before it goes near heat.
165F is the instant-kill number, but pasteurization is a curve of time against temperature, not a single point. The same 7-log Salmonella reduction happens in about 45 seconds at 155F, about 3 minutes at 150F, and roughly 9 minutes at 145F. A breast that reaches 155F and rests for a couple of minutes has been pasteurized. The catch is that you need a real thermometer and you need to know the meat stays there, which is why 165F is the number given to the general public.
Yes, and dry-brining is simpler than wet. Use 0.75-1% salt by weight — about 1 teaspoon of Diamond Crystal kosher per pound — rub it on, and leave it uncovered in the fridge anywhere from 4 to 24 hours. Salt dissolves the myofibrillar proteins so they hold onto more water when they contract, cutting cooking losses by several percent, and it seasons the interior instead of just the surface. A wet brine at 5-6% salt for 30-60 minutes does much the same thing but leaves the surface wet, which costs you browning.
Thigh, unless you're pounding the breast flat first. A grill runs 500-700F at the grate, which is a huge gap between surface and center, and breast has a 5-degree window between done and ruined. Thigh has fat and collagen that keep improving up to 185F, so the same fire that destroys breast is doing something useful to thigh. If you want breast on a grill, butterfly it to half an inch, use a two-zone setup, and pull it at 150F.