Lay all 4 chicken breasts, meat side down, in small (8-inch) skillet.
Add enough water, with chicken bouillon, added to just cover chicken.
Add onion over top of chicken.
Sprinkle with tarragon.
Bring to boil and reduce heat to medium.
Cover skillet with well-fitting lid and cook approximately 30 to 45 minutes or until chicken is done. Add a little water if necessary to replace any lost in steam.