Béarnaise Sauce | Warm Tarragon Emulsion with Pasteurized Egg Yolks

Put the vinegar, finely chopped shallot, tarragon stems, and crushed whole peppercorns in a small saucepan. Simmer over low heat until the liquid has reduced to about one-third and only a thin layer remains on the bottom of the pan. All of the sauce’s acidity comes from the grape vinegar; do not dilute the reduction with another liquid.

Add the pasteurized egg yolks to the reduction. Because this sauce contains uncooked egg, pasteurized eggs are essential; do not make it with eggs whose packaging does not say pasteurized. Set the bowl over gently simmering water without letting its bottom touch the water. Whisk constantly: the mixture will foam, then double in volume and thicken until the whisk’s trail remains for one second. Remove the bowl from the heat as soon as the trail begins to hold.

While whisking constantly, slowly drizzle in the melted, lukewarm butter in a thin stream. Do not pour in the milky solids that have settled at the bottom of the butter; they can make the sauce break more quickly. Stir in the finely chopped tarragon leaves and salt. The sauce should coat the back of a spoon and fall in a continuous ribbon. Serve immediately.