2 egg yolks
½ tsp white wine vinegar
splash ice cold water
Melt 125g butter in a saucepan. Keep the butter warm. Put 2 egg yolks, 1/2 tsp white wine vinegar, a pinch of salt and a splash of ice-cold water in a metal or glass bowl that will fit over a small pan. Whisk for a few minutes then put the bowl over a pan of barely simmering water and whisk continuously until pale and thick, about 3-5 minutes.
Remove from the heat and slowly whisk in the melted butter, bit by bit until it’s all incorporated and you have a creamy hollandaise. (If it gets too thick, add a splash of water.) Season with a squeeze of lemon juice and a little cayenne pepper. Keep warm until needed.