Put the tarragon, shallot, peppercorns, white wine vinegar and vermouth into a saucepan and cook over a medium to high heat. Allow to simmer and reduce until there are one and half tablespoons of liquid remaining. Take the pan off the heat and set aside.
Lightly beat the egg yolks in a bowl. Strain the tarragon reduction into the egg yolks and discard the leftover tarragon and shallots.
Add the melted butter and water to the egg yolks and whisk everything together with a fork or small whisk.
Once the béarnaise is cooked, pour it into a clean bowl and whisk together to form a smooth sauce. If I am cooking a steak, I like to leave the béarnaise warm over a saucepan of just boiled water on a low heat until I am ready to serve. If the béarnaise gets too thick, add a few drops of boiling water to thin it out.
Sous Vide Steak
2 (8 ounce/240g) steaks
Salt and pepper, to taste
1 tablespoon (15 ml) peanut oil, to fry
Fill and preheat the SousVide Supreme to your preferred degree of doneness (120F/49C rare; 134F/56.5C medium rare; 140F/60C medium; 150F/65.5C medium well)
Pat the steaks dry with kitchen paper (paper towel) and season them on both sides with salt and pepper. Smoked salt is a nice alternative to give the steak a slightly smoky crust.