You will need
4 egg yolks
1 tsp truffle oil
1 tsp white-wine vinegar
150g butter, melted
Salt and pepper
Put the egg yolks, truffle oil and white-wine vinegar in a metal bowl. Place the bowl over a pan with gently simmering water, whisk the eggs and slowly add the butter – do not scramble the eggs.
Remove the bowl from the heat every 30 seconds (you want to cook the yolks). If the hollandaise becomes a little too thick, add a little warm water.
To finish, season with salt and pepper.