Rub the chicken breast halves with salt and ginger. Discard the ginger. Lightly coat the chicken with flour.
Heat 3 tablespoons of olive oil in a large frypan over medium-high heat. Brown the chicken in the hot oil until it is not quite done but the skin is browned and crisp. Remove from frypan and set aside.
Heat remaining 3 tablespoons olive oil in the frypan then saute onion until soft and translucent. Use the chicken stock to deglaze the frypan. Stir in the cream and sour cream. Reduce heat to low and simmer until the mixture has reduced a little. Stir in the white wine.
Add the tarragon to the frypan and place chicken breasts on top of tarragon. Cook over low heat, spooning sauce over chicken, until the sauce has become very thick, the chicken is no longer pink and its juices run clear.