Heat oil & butter
Seal chicken quickly on both sides (or whether you brown or not is up to you - I like them browned)
Add vegetables, spring onions and tarragon to chicken.
Cook for 2 min.
Add first batch of wine or stock to chicken
Bring to boil
Cover and poach gently for until chicken is tender (but cooked), turning occasionally (20 min if you only sealed the chicken and 15 min if you browned it)
Transfer chicken and vegetables to a warm platter, cover and keep warm.
Top up remaining pan juices with wine so it is at least 1 cup
Boil pan juices until slightly syrupy
Stir cream, salt and pepper, and mustard into sauce.
Boil until slightly thickened.
Return chicken and vegetables to pan, turn into sauce and heat together briefly.
Sprinkle Paprika or tarragon leaves over chicken