This classic sauce is a tradtional accompaniment for steamed fresh asparagus. It requires your undivided attention and a lot of whisking, but it's well worth it. The resulting sauce is heavenly and much better than anything bought from a shop.
Time: 20 minutes
40ml white wine vinegar
1 small shallot, peeled and chopped
a few sprigs of French tarragon
1 bay leaf
200g unsalted butter
3 small egg yolks
freshly ground white pepper
Put the wine vinegar, water, tarragon, bay leaf, shallots and peppercorns into a small pan and bring the mixture to the boil. Let it boil for a few minutes, until the liquid has reduced to no more than a dessert spoonful. Strain the liquor through a sieve and let it cool.
Next, clarify the butter by melting it slowly in a pan and simmering for five minutes over a very gentle heat. Remove it from the heat, let it cool a little and then pour off the clarified butter and discard the whey.
Add the egg yolks and half of the vinegar reduction to a heatproof bowl and set it over a pan of simmering water. Whisk together, until the mixture begins to thicken and become frothy. Now start to slowly add the butter in a trickle, whisking all the time.
Be careful, as if you add the butter too quickly, the sauce will separate. If the sauce does starts to curdle or split, you can rescue it by scraping the mixture into a clean bowl and whisking in 1 tbsp ice-cold water, then continue whisking in the remaining butter.
When you've added two thirds of the butter, taste the sauce and add a little more of the vinegar reduction, then add the remaining butter. Everyone's preference is different, but the aim is to get a buttery, tangy sauce that's not too vinegary. Season with salt and pepper to taste, cover, and keep in a warm place until you're ready to serve it.
Steaming the asparagus should only take three or four minutes in a pan of well salted boiling water. Here's how to cook steamed asparagus
Serve the asparagus with the sauce ladled over the top, or in individual bowls for dipping.