1. Heat an inch or two of water in a saucepan over a medium heat.

2. Combine the egg yolks and the cold water in a glass or stainless steel bowl (not aluminium or silver) whisk for a minute or two, until the mixture is light and foamy. Whisk in a couple of drops of lemon juice, too. The water in the saucepan should have begun to simmer.

3. Set the bowl directly atop the saucepan of simmering water. The water itself should not come into contact with the bottom of the bowl.

4. Whisk the eggs for a minute or two, until they’re slightly thickened. Remove the bowl from the heat and begin adding the melted butter (this should be warm, not hot) slowly at first, a few drops at a time, while whisking constantly. If you add it too quickly, the emulsion will break.

5. Continue beating in the melted butter.

6. As the sauce thickens, you can gradually increase the rate at which you add it, but at first, slower is better.

7. After you’ve added all the butter, whisk in the remaining lemon juice and season to taste with salt and cayenne pepper.

The finished hollandaise sauce will have a smooth, firm consistency. If it’s too thick, you can adjust the consistency by whisking in a few drops of warm water.