Preparation:
To half a pint of good stock add two good sprays of fresh tarragon, simmer for quarter of an hour in a stewpan and keep the lid on.  

In another stewpan melt one ounce of butter and mix it with three dessert-spoonsful of flour, then gradually pour the stock from the first stewpan over it, but take out the tarragon. Mix well, add a teaspoonful of finely chopped tarragon and boil for two minutes.