In a small saucepan, combine the tarragon, shallots, vinegar and wine over medium-high heat. Bring to a simmer and cook until it has reduced by half. Remove from heat and set aside to cool.

In a blender, pulse the yolks and Bearnaise reduction together. While the blender is running, add 1/3 of the butter in a slow steady stream. Once it emulsifies, turn the blender speed to high and add the remaining butter. Add vanilla and chives, if using, and season with salt and pepper. Pour into a slightly warmed bowl and set aside in a warm place until ready to serve. You can make this sauce in a warm bowl with a hand-held whisk if you prefer. It’s a little more work but not significantly so.