Blend the egg yolks in a blender or food processor until well mixed.

In a small saucepan, heat the lemon juice and vinegar and, with the motor running, pour in a slow thin stream into the yolks.

In the same saucepan, melt the butter until foaming. Once again, with the motor running, very slowly add the butter to the egg mixture. The slower the better! Season with salt and pepper.

Trim 2 – 3 cm from the bottom of the asparagus before peeling. Blanch in salted boiling water for 3 – 5 minutes. Drain and serve immediately with hollandaise and a good crack of black pepper.

Note: Cooking time will vary depending on the thickness of the asparagus spears.