Thinly slice the banana shallot and place into a medium saucepan with the white wine and vinegar.
Pick the leaves of the tarragon and keep to the side. Put the stalks into the saucepan and place on a medium high heat. Reduce the liquid by two thirds, roughly 15 minutes.
To clarify the butter, place it into a clean saucepan and melt on low heat. Allow the solids to sit at the bottom (they will not be added to the sauce).
Finely chop the tarragon, chervil, parsley, and chives. Keep to the side.
In a bowl place the egg yolks and cooled wine reduction. Whisk to fully incorporate. Whilst continuously whisking slowly pour in your very hot butter. If your sauce is starting to split, add in a teaspoon of ice-cold water. If it’s getting too thick add a teaspoon or two of the hot water. Continue to whisk till fully emulsified.
Once all the butter is added, stir through your finely chopped herbs. Season with salt, pepper, and lemon juice to taste. Add more of the onion reduction too if you like it. If you have cooked a steak, pour in the hot beef pan drippings whilst whisking for extra flavour.
