Quick Chicken with stalks

4 -6 chicken thighs 2 (14 1/2 ounce) cans diced tomatoes 1 medium onion , coarsely chopped 1 stalk celery , sliced 1 carrot , sliced 1/2 green pepper 1/2[...]

1 tablespoon olive oil 1 tablespoon butter 1/2 onion , chopped 1 carrot , peeled and chopped 1 stalk celery , chopped 1 chicken breast , diced 1 garlic clove[...]