This is a lovely lemony sauce with a distinctive sorrel tang that goes extremely well with baked white fish such as sole, or the local river trout I am lucky to be given. It is best served and eaten as soon as it is made – don’t keep it for more than an hour after making it.
240 ml warm clarified butter
4 egg yolks
2 tbsp lemon juice (1 small lemon)
1 tbsp cold water
Rock salt, to taste
Cayenne pepper, a pinch (or a dash of hot sauce)
A handful of finely chopped sorrel leaves
Heat around 5 cm of water in a double boiler saucepan over a medium heat, keeping back the bowl
Whisk the egg yolks and the cold water in the bowl (glass or stainless steel) for two minutes, until light and foamy. Then whisk in a couple of drops of lemon juice.
The water in the saucepan should have started simmering. Put the bowl back onto the saucepan, sitting above but not touching the simmering water. Whisk the eggs for a minute or two, until they start to thicken. Remove the bowl from the heat and start adding the melted butter slowly, a little at a time, while whisking constantly. If you add it too quickly, the mixture will curdle. Carry on whisking in the melted butter. As the sauce thickens, you can increase the speed at which you add the butter.
After all the butter is added, whisk in the rest of the lemon juice, add some ground rock salt and cayenne pepper or hot sauce. Then add the finely chopped sorrel. The sauce should now have a smooth, firm consistency. If it’s too thick, you can thin it a little by whisking in a few drops of warm water.
Spoon over the baked fish and serve immediately.
A nice side dish to go with this is creamed, mashed potato with chopped ground elder (goutweed) added which give it a mild celery flavour. Also some finely sliced – the size of skinny french fries – burdock root, stir-fried until just tender in a very light soy sauce.