Make bearnaise reduction: in a small sauce pan, over medium high heat, combine 1/2 of tarragon, shallots, vinegar and wine and bring to a simmer. Cook until reduced by half. Remove from heat and set aside to cool.

Blend yolks with bearnaise reduction in a blender, or with an immersion blender, with blender running on a medium speed, add 1/3 of melted butter in a slow steady stream. Once it has emulsified {blended in} turn blender up to high and add the rest of the butter. Add remaining tarragon, season with salt and pepper, blend quickly once more and set aside. Keep warm until serving

Makes about 1 cup