1. In a large heavy skillet or ideally a Dutch oven, heat the butter and olive oil on medium heat until the butter melts. Add the chicken pieces and cook until browned on all sides.
2. Meanwhile, remove all of the leaves from the tarragon sprigs. Place half of the leaves and the white wine in a small saucepan and boil on medium heat until the liquid is reduced by half - about five minutes.
3. When the chicken is browned all over sprinkle with salt to flavor, then sprinkle with the flour and stir to coat evenly. Add the reduced wine mixture and the chicken stock to the chicken and stir to combine. Put on low heat, cover and cook for one hour.
4. Snip the rest of the tarragon leaves into small pieces and combine with the crème fraîche or cream and the lemon juice. About five minutes before serving, stir this mixture into the chicken and warm through.

Makes 8, 1 piece servings.

Serve with rice, couscous, or pasta (there is quite a bit of sauce).