Makes 2–3 servings
- Add egg yolks, lemon juice and hot water to a cylindrical container that only just fits the head of an immersion blender.
- Chop butter into chunks and heat butter in microwave on high until boiling (about 2 minutes).
- Insert immersion blender into container and start blending. Gradually pour in melted butter over 30–60sec. Gently raise the blender as you go. There will be some whitish proteins at the bottom of the butter, discard them.
Use it straight away; it won’t keep.
— J. Kenji López-Alt