01. In a blender, mix the egg yolks and lemon juice until smooth.
02. While the mixer is running, slowly pour in the melted butter in a thin stream until the sauce is thick and creamy.
03. Add salt and black pepper to taste and whisk again.
04. If the sauce is too thick, add a tablespoon of warm water at a time and whisk to desired consistency.
05. Serve immediately or keep warm in a bain-marie until ready to use.