• Place the shallots with the wine vinegar into a small saucepan and simmer until it has reduced and you have one tablespoon left.
• Place a basin over a pan of hot water on a low heat - this is a bain marie.
• Sieve the contents of the pan - the shallots and wine vinegar - into the basin.
• Add one tablespoon of water and ½ oz butter to the wine vinegar.
• Add the beaten egg yolks and begin to whisk them with a small whisk until the sauce begins to thicken.
• Do not allow the sauce to boil, keep it simmering, then add the rest of the butter, whisking it in a little bit at a time until it has all been incorporated into the sauce.
• When the sauce is lovely and creamy and smooth, put in the tarragon and parsley herbs and taste it to see how much salt and pepper you need to add to it.
• Serve your sauce warm and not hot as if heated too much, it will curdle and separate.

This is how you make a very ordinary dish into a special occasion!