Serves 2 – 1 egg yolk – can easily be multiplied.

• 1 free-range, organic egg yolk – as fresh as you can get it
• a splash of cold water, about 1 tsp
• 55g/2oz good quality butter, fridge-cold and diced
• a splash of lemon juice, about ½ tsp but to taste
• Season, to taste

Set a clean bowl above an 2.5cm/1″ of barely simmering water. It’s important water doesn’t come into direct contact with the bottom of the bowl.

Place 1 egg yolk in the bowl, together with a splash of cold water and whisk together.

Add a cube of cold butter. Whisk continuously. In order to emulsify everything you need to keep it all moving. As soon as your cube of butter has been incorporated, add the next. And the next.

Before your eyes your sauce will thicken.

When all the butter has been incorporated, add a splash of lemon juice. Season to taste.

Eat.