1. Cream about one tablespoon of the chopped tarragon into the butter either with a pestle and mortar or with a spoon in a small bowl.
2. Season this with salt and pepper and stuff the chicken with this mixture.
3. Place the chicken in a heavy bottomed roasting pan on it's side.
4. Place in a pre-heated oven at  400°F/200°C/Gas 6
5. Roast for about 15 minutes then turn the chicken on it's other side, basting with the melted butter.
6. Continue to roast the chicken with the occasional turn and basting with the tarragon butter until it is cooked about 1 to 1.5 hours depending on the size of your chicken or until it reaches an internal temperature of 165°.
7. When cooked, remove from pan and leave to stand on a warmed plate while you make the sauce.

How To Make The Sauce

1. Make a beurre manié by working a teaspoon of butter and a teaspoon of flour together.
2. Place this mixture into the juices that are still in the pan, stirring constantly with a whisk.
3. Gradually add the cream to this mixture with two teaspoons of freshly chopped tarragon leaves.
4. Bring the mixture to a boil and as soon as it thickens it is ready to serve and pour over the chicken. You can taste it at this stage and add salt and pepper if needed.
5. While the chicken is being carved keep the sauce warm.