Yield 1 cup
In a small saucepan, add vinegar, wine, shallots and 1 TB. tarragon leaves with a little sea salt and pepper. Bring to a boil and simmer over medium heat until liquid is reduced to about a tablespoon. Cool slightly.
Transfer the cooled mixture with the egg yolks into a blender. Blend 30 seconds.
With the blender on, slowly pour the hot butter through the opening in the lid. Add the remaining tablespoon of tarragon leaves and blend for only a second.
If the sauce is too thick, add a tablespoon of white wine to thin.
Note: To make the sauce in advance, prepare an hour before serving and allow it
to sit in the blender. Before serving, add 1 tablespoon of the hottest tap water
and blend for a few seconds.
Adapted from Ina Garten