Step 1

Place a small saucepan over medium heat, add the vinegar, wine, peppercorns, and onion. Reduce until 2-3 tablespoons of liquid remain.

Step 2

Strain out the onion and peppercorns and pour the liquid into a heatproof bowl. Add the egg yolks.

Step 3

Melt the butter until the milk fat (white liquid) has separated from the yellow butter. Set aside.

Step 4

Place the bowl over a saucepan of simmering water and start whisking.

Step 5

Continue to whisk until the mixture is thick and foamy and creates thick ribbons when the whisk is lifted.

Step 6

Remove the bowl from the heat and slowly pour in the hot butter while whisking, ensuring that the milk fat is left behind. This step is similar to making mayonnaise - if you add the butter too quickly the sauce will split.

Step 7

Whisk in the salt, pepper, and tarragon.

Step 8

Serve immediately or keep warm until needed.