• 4 tablesp. (¼ cup) tarragon vinegar
• 4 tablesp. (¼ cup) dry white wine
• 2 teasp. finely chopped shallots
• a pinch of freshly ground pepper
• 1 tablesp. freshly chopped French tarragon leaves
• 2 egg yolks (preferably free-range)
• 4–6 ozs (110–150 g/1–1½ sticks) butter approx., salted or unsalted depending on what it is being served with

If you do not have tarragon vinegar to hand, use a wine vinegar and add some extra chopped tarragon. Boil the first four ingredients together until completely reduced and the pan is almost dry but not browned. Add 1 tablespoon of cold water immediately. Pull the pan off the heat and allow to cool for 1 or 2 minutes; whisk in the egg yolks and add the butter bit by bit over a very low heat, whisking all the time. As soon as one piece melts, add the next piece; it will gradually thicken. If it shows signs of becoming too thick or slightly ‘scrambling’, remove from the heat immediately and add a little cold water if necessary. Do not leave the pan or stop whisking until the sauce is made. Finally add 1 tablespoon of freshly chopped French tarragon and taste for seasoning.

If the sauce is slow to thicken it may be because you are excessively cautious and the heat is too low. Increase the heat slightly and continue to whisk until the sauce thickens to a coating consistency. It is important to remember, however, that if you are making Béarnaise Sauce in a saucepan directly over the heat, it should be possible to put your hand on the side of the saucepan at any stage. If the saucepan feels too hot for your hand it is also too hot for the sauce.

Another good tip if you are making Béarnaise Sauce for the first time is to keep a bowl of cold water close by so that you can plunge the bottom of the saucepan into it if it becomes too hot.

Keep the sauce warm in a bowl over warm water or in a thermos flask until you want to serve it.