Remove chicken breasts from refrigerator 20-30 minutes before cooking to take the chill off. Pat dry with paper towels. If breasts are very thick (over 1 inch), butterfly or gently pound them to an even thickness of approximately ¾ inch.
Place chicken breasts in a single layer in a wide, shallow pan. Avoid overcrowding; the breasts should not overlap.
Add cold water to the pan until breasts are submerged by ½ inch. Add salt and any chosen aromatics.
Place pan over medium heat and slowly bring the water to the target temperature of 170-180°F (77-82°C). Small bubbles should form around the edges, but the water should never reach a full simmer.
Once the water reaches 170-180°F, reduce heat to maintain this temperature range. Do not allow the water to boil.
Cook chicken according to thickness (see timing chart in article). For standard 1-inch thick breasts, this is typically 10-12 minutes.
When cooking time completes, remove pan from heat, keeping chicken in the liquid. Cover and let rest for 10 minutes to complete carryover cooking.
Insert a thermometer into the thickest part of the breast. It should register 165°F (74°C).
Using a slotted spoon or tongs, transfer chicken to a cutting board. Allow to rest for 5 minutes before slicing or storing.