Dice the shallot

Heat the olive oil in a small pan and glaze the shallot at medium fire for 5 minutes

Add the vinegar, the wine, the tarragon and add the salt and pepper

Let simmer for 15 minutes with the lid on (low heat) and then increase the fire a bit and take the lid off to let the vinegar and alcohol cook off a little. Aim to keep 1.75 oz (50 g) liquid left

Strain the mixture through a small sieve and press with a spoon the shallot/tarragon mixture in the sieve to release all its juices. Let the gastrique cool down to room temperature and reserve

Melt the ghee to approximately 120 F (50 C). Find instructions to make ghee from butter easily yourself, under remark 1.

Bring egg yolks and gastrique to room temperature. Thereafter mix them in a stainless steel bowl or a metal pan with a whisk ( I prefer a thin bottomed pan or bowl as it is more responsive to the heat that is added or taken away

Heat the bowl au bain marie under constant whisking. After a few minutes the temperature will approach 163 F (73 C) and the mixture will become thicker and more viscous. Continue the whisking for a few tens of seconds, so that you whisk a lot of air in, making an in-situ sabayon. Be careful not to overheat.