Place chicken in a small pot and season with salt and pepper. Add enough cold water to cover the chicken by 1-inch. Place pot over medium-high heat and bring to a boil. Reduce heat to maintain a gentle boil and cook 10-12 minutes, until a meat thermometer inserted into the thickest part of the chicken reads 165 degrees. Remove chicken to a plate and tent with foil. Rest 5 minutes.
If cooking multiple chicken breasts, increase salt and pepper accordingly and try to use a pot large enough to fit them in a single layer. If there is a lot of overlap, or you can't fit them in a single layer, you will need to increase cook time.To cook from frozen, increase cook time once boiling to 25-30 minutes, and use a thermometer to ensure meat is cooked through.