Cut 12 tablespoons of the butter into cubes and place in a small saucepan or, preferably, a heat-proof glass measuring cup.
Put the saucepan, or cup, in a larger saucepan and pour simmering water around it.
Bring water to simmer and let simmer until butter is melted.
Skim off and discard the white scum that rises to the top of the butter.
In a saucepan, combine shallots, tarragon, vinegar, 2 tablespoons of the water and pepper; bring to the boil; cook until liquid is almost completely evaporated.
Take care that solids do not scorch or burn; remove from heat and let cool.
Add the remaining 1 tablespoon water along with the egg yolks.
Place the saucepan over very low heat and start beating with a wire whisk.
Stir rapidly until the mixture is thickened and sauce like.
Take care that the sauce does not overheat or the yolks will curdle.
Remove from the heat and beat in the remaining 1 tablespoon cold butter.
Off heat, add the golden liquid butter, 2 or 3 tablespoons at a time, beating well after each addition.
Discard the white liquid that remains at the bottom of the melted butter.
