3 Tablespoons Finely Chopped Fresh Tarragon
2 Medium Shallots, Finely Minced
½ Cup White Balsamic Vinegar
1 Teaspoon Coarse Sea Salt
½ Teaspoon Coarsely Ground Black Pepper
4 Large Egg Yolks
20 Tablespoons (2 ½ Sticks) Unsalted Butter, Melted
1 Tablespoon Fresh Squeezed Lemon Juice
Place the tarragon, shallots, vinegar, salt and pepper in a small sauce pan and reduce the liquid over medium heat until there are only a few drops left in the pan. Set aside to cool to room temperature.
Once the reduction is cooled place in a mixing bowl and whisk in the egg yolks and lemon juice. Set the bowl over a pan of simmering water and whisk until the eggs are warm and the mixture has doubled in volume. Do not let the bottom of the bowl touch the simmering water.
Very slowly and continually whisk in the melted butter a tablespoon at a time to emulsify the mixture. Remove the bowl from the pan occasionally so as not to scramble the eggs. Once all the butter is incorporated taste for seasoning and add more salt or lemon juice if needed. If the sauce is too thick for your liking, whisk in a tablespoon of warm water to thin it out. Serve immediately.
This sauce cannot be made too far in advance and must be kept in a warm place until served.