Béarnaise Sauce

1. Finely chop the shallot and half of the tarragon, then combine them in a small saucepan with the tarragon vinegar and white wine. Simmer gently over medium heat until the liquid has reduced to about 2 tablespoons, then strain the reduction into a heatproof bowl and let it cool slightly.
2. Cut the butter into cubes and melt it slowly in a separate pan until fully liquid but not browned, then keep it warm off the heat. Skim off and discard the white foam if you want a clearer sauce.
3. Add the egg yolks and the tablespoon of cold water to the bowl with the cooled reduction and whisk until smooth and pale.
4. Set the bowl over a pan of barely simmering water, making sure the base does not touch the water, and whisk constantly for 3 to 5 minutes until the yolks thicken to a ribbon that holds a trail; do not let the temperature exceed about 70 C or the eggs will scramble.
5. Remove the bowl from the heat and, whisking continuously, pour in the warm melted butter in a thin steady stream until the sauce is thick, glossy and emulsified.
6. Stir in the remaining chopped tarragon, then season with salt and a small pinch of cayenne pepper to taste.
7. Serve immediately while warm; if the sauce stiffens, whisk in a few drops of warm water to loosen it. Keep it in a warm spot rather than over direct heat and do not reheat, as it will split.

You'll use: Saucepan · Pan · Large pot · Whisk