Place the chicken breasts in a medium frying pan or saucepan with a lid. You need a pan that they just fit into; you don't want a lot of space around the chicken.
Season the chicken breasts with salt, pepper and your choice of fresh or dried herbs.
Cover the chicken with the stock and put the lid on the pan.
Bring the stock to the boil.
Turn the heat back and simmer the chicken breasts over medium heat for 10 minutes, keeping the lid on the pan.
Turn the heat off and let the chicken sit in the hot liquid for 20 minutes. Again, keep the lid on the pan.
Remove the chicken breasts carefully from the hot stock. Check the chicken is cooked through and no pink remains inside. Either use the chicken breasts immediately or cool and chill or freeze.