Peel and slice the shallot very thinly.
Put the white wine, shallot, and bay leaf in a small saucepan.
Leave to cook over a medium flame until the liquid has halved in volume.
Filter the wine and shallot reduction and leave to cool.
Melt the ghee butter.
Break the 2 egg yolks into a saucepan, do not throw away the shell, you will need it as a measuring cup.
Place water in a saucepan larger than the one on the stove to cook the eggs in a bain-marie.
Add 2 tablespoons of the wine reduction to the eggs and whisk vigorously.
Place the saucepan over the pan of water and continue cooking in a bain-marie, while continuing to whisk the eggs.
There are two ways to tell when the mixture is ready: The first is more scientific, by checking with a thermometer that the mixture reaches a temperature of 82°C. The second, more empirical way is to turn off the heat when the cream starts to “write”, that is, when you can draw with the mixture on the whisk.
Remove the mixture from the heat and add the ghee butter, emulsifying it slowly. Season with salt and pepper and add a few drops of lemon, mixing the mixture well.
The sauce is now ready and can be served with the asparagus.
It is also delicious served with salted sea bass or any other delicate white fish.