This sauce goes very well with dishes like eggs Benedict - pour it over poached eggs and toasted muffins with some grilled bacon and leaves of spinach, or replace the bacon and spinach with slices of smoked salmon. You've got to work quickly with this, though - practise makes perfect!

Firstly, get your ingredients ready. You'll need three tablespoons of water, four egg yolks, two level tablespoons of butter, a teaspoon of white wine vinegar or lemon juice, and a teaspoon or so of mustard. You might also want to try adding a little ground paprika.

Make a double-boiler by putting a large glass bowl in the top of a saucepan with a couple of inches of boiling water in the bottom - the bottom of the bowl should be a couple of cm above the surface of the water - on a medium hob. When the bottom of the bowl gets warm, add the three tablespoons of water.

Whisk your egg yolks into this and keep stirring with the whisk until the mixture starts to foam. Meanwhile, melt the butter in a ramekin dish in the microwave.

When the yolks are paler and starting to foam, add the butter a couple of drops at a time, stirring continuously. The sauce will thicken and carry on foaming, going a lovely rich yellow. When all the butter has been added, add the vinegar to thin the sauce a little - a drop at a time - and stir over the heat for another minute or so. Remove from the heat and whisk in the mustard and paprika. Serve immediately.