This is a traditional bearnaise sauce where an emulsion is formed by slowly whisking butter into egg yolk. It can take some practice to master, but when it comes together, it is a rich and creamy addition to a perfectly cooked steak that elevates your cooking skills.
In a small pan preheated over medium heat, add the white wine, vinegar, and shallot.
Add the tarragon and let the liquid reduce to about one tablespoon, stirring occasionally.
Remove from heat and set aside to cool.
Make the emulsion:
Set the ghee in a pot over low heat. If your range doesn’t hold an even low temperature, consider sliding the pot only to cover half of the flame to keep the ghee liquified but not simmering at all.
Meanwhile, whisk the egg yolks with the water in a small pot.
Place over low heat, and while whisking continuously, add the liquified ghee one tablespoon at a time, ensuring it is fully incorporated before adding the next.
After the 6th or 7th tablespoon of ghee, turn off the heat and continue to mix in one tablespoon a time, whisking to emulsify.
When all of the clarified butter is fully emulsified into the egg, you should have a smooth, luscious sauce that is thinner than mayonnaise but still coats the back of a spoon.
Stir inthe Dijon mustard.
Remove the tarragon sprig from the shallots and mix it into the sauce. Add the fresh minced tarragon and season with salt and coarse ground black pepper to taste.
Serve immediately.
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Notes
Instead of setting the eggs in a pot directly over a low flame, you could use a bowl of simmering water in a double boiler if you have one. Use caution not to let the bottom of the bowl touch the boiling water.We recommend a dry white wine for this.If the sauce is too thick, stir in a tablespoon of water to smooth it.This sauce is also wonderful over fish, chicken, or veggies like asparagus.If you aren’t serving the sauce right away, store it in a thermos or hot liquid container with a lid to keep it warm until ready to serve, within an hour or two. You want to avoid reheating this sauce over direct heat. If needed, it can be reheated over a double boiler, whisking just to bring the sauce to temp.If the sauce splits, remove the sauce from the heat and add one tablespoon of water. Whisk to bring the sauce back together. Be patient, but if that doesn't work, then see our next tip.