6 oz/180 g butter
12 fl oz/375 ml champagne (don't buy cheap)
4 shallots (very finely chopped)
4 egg yolks
salt and pepper
few drops of lemon juice
Heavy based saucepan (NOT ALUMINIUM)
Open the oysters and put the meat into a bowl with the lemon juice.
Scrub the shells clean and set them flat on four individual ovenproof plates filled with rock salt to stop them from tilting.
Drain the oysters, reserving the liquor (juice) and set them on the shells.
For the sauce: melt the butter and skim the froth from the surface, then allow it to cool until hand-hot. Meanwhile, boil all but 2 fl oz / 60 ml of the champagne with the shallots in a heavy pan until reduced to 2-3 tablespoons. Cool slightly, then whisk in the egg yolks and reserved oyster juice. Continue whisking to a mousse, working on and off the the heat for 3-4 minutes until it is thick enough to leave a ribbon trail when the whisk is lifted. Remove the pan from the heat and whisk in the hot butter, first a little at a time then in a steady stream, leaving they whey at the bottom of the pan. NOTE: if the butter is too hot or added too quickly the sauce will separate. Flavour the sace with salt to taste, pepper if desired and the lemon juice.
It can be kept warm in a water bath up to 20 minutes if preparing in advance.
Just before serving, stire the rest of teh champagne in to the sauce and spoon it over the oysters. Grill until brown for 3-5 minutes and serve immediately.