Fill a medium sized saucepan approx 1/3 full with water and put on to boil.

Place the butter in a clear microwave safe dish and microwave on high for approximately 5 minutes, (until the butter has separated).

Pour the clarified butter off the top into another container and discard the white liquid left at the bottom.

Reheat the clarified butter a further 2 minutes and skim any impurities off the surface.

In a large stainless steel mixing bowl place the egg yolks with a few drops of water and whisk together and then whisk in 2 tsp of vinegar.

Place the bowl over the saucepan of boiling water and whisk until the egg yolks have thickened and become lighter in colour.

Remove the bowl from the pan and place it on a folded slightly wet towel.

Gradually add the still warm clarified butter in a steady stream whilst whisking the eggs.

Keep adding the butter as long as the eggs will hold it, (if the sauce gets a slightly shiny oily appearance, hold off with adding the butter and continue to whisk until the oily appearance has disappeared).

Once all the butter has been incorporated add the lemon juice, (if the sauce appears too thick whisk in 1 tbsp of tepid water).

Season to taste and serve (the sauce can be kept in a slightly warm spot or in a Bain Marie).