Melt butter in saucepan over low heat. Set aside and keep luke-ish, about 50° C
Add vinegar, shallots, pepper, water, tarragon- and parsley-stems into a heavy-based saucepan. Bring to a boil and reduce to three tablespoons. Strain, discard solids and set aside until luke-ish, about 50°
Add egg yolks to the liquid and whisk constantly over low heat (or suspended over, not touching, a pan of simmering water) until the mixture starts to thicken. This should occur at 65-70° C
Remove saucepan from heat and add butter, a few drops at a time at start and after having dropped in a few tablespoons, in a steady stream, whisking continuously, until the mixture is thick and smooth
Fold in the tarragon, parsley and chervil and season, to taste, with salt, Tabasco and lemon juice
Keep and serve room temperatured
Recipe Notes
The sauce will improve in taste if it is allowed to sit for an hour or two
If yolk-reduction-mix thickens too much (scrambled egg style) before adding butter – discard and start from scratch
If sauce is too thick, dilute with water at same temperature as sauce – or it will separate
If sauce is too thin, try adding dried herbs
The sauce will thicken when temperature reduces
If the sauce is about to separate – add a dash of cold water
Don’t re-heat – it will separate
If sauce separates when adding in the butter: whisk a new yolk over low heat (65-70° C until foamy) and drip in the separated sauce whisking continuously
If sauce separates when reheating: reduce 5 tablespoons of double cream by 50%, remove from heat and drip in the separated sauce whisking continuously