In a small saucepan, combine vinegar, wine, shallots, 1 T of the tarragon, 1/4 tsp salt and 1/4 tsp pepper. Bring to a boil until the mixture has reduced to only a few tablespoons.

Cool slightly and transfer to a blender. Add the egg yolks and 1 tsp salt. Run for 30 seconds.

While blender is running, slowly pour in the melted butter. Add remaining tarragon and shut off blender.