Heat the oil in a pan, season the chicken, brown for approx. 3 mins. with the skin side down, turn and continue frying for approx. 1 min. Add the diced bacon and fry, stirring, for approx. 1 min. Add the celery, onions and butter and sauté for approx. 3 mins. Add the white wine and salt, bring to the boil, then simmer for approx. 2 mins. Add the butter and heat over a medium heat for approx. 5 mins., stirring occasionally. Add the tarragon, mix together.