For such a killer sauce it's kind of a sidenote in Mastering the Art. Dinah has a great kitchen with beautiful knives and pans. She all ready reduced the fresh and dried tarragon in the white wine, wine vinegar and shallots, and strained it...pictured in the foreground.
I won't go through all the details...see pages 84-85 in Mastering the Art of French Cooking. Dinah got a fabulous texture this time, rich and smooth.
It was like butter and we ate it all...is that a piece of Sydenstricker I see?