Break off the artichoke stalks. Put the heads into a large pan, cover with water and bring to the boil. Cover and cook for 30—40 minutes until a leaf pulls out easily. Drain and cool.
Meanwhile, to prepare the lobster yourself, you will need a cleaver or a large heavy knife. Lay the lobsters with their heads away from you, shells uppermost, and halve lengthways with a good strong blow down the centre of the back. From each one remove and discard the little sac near the head (this is the stomach), pull out the thin black vein running along the body (the gut). Remove the coral if there is any, and put it into a bowl.
Scrape out the pale green soft meat (the tomalley or liver) and add to the coral, then remove the soft pinky head meat and add that to the bowl. The feathery gills should be taken out and discarded, but the soft flesh underneath them can be added to the corals.
Now extract the tail flesh and put it into a separate dish. Crack the claws with a sharp blow, pull out the meat and add to the tail flesh. If you wish, you can also extract the meat from the next largest pair of legs, but these, and the shells, can make an excellent soup. Scrub the shells and dry. Chop the tail meat into chunks.
When the artichokes are cool enough to handle, pull off the leaves (keep them to serve with a vinaigrette), then scrape off all the furry ‘chokes’ and trim and chop the hearts.
Melt 50 g/2 oz of the butter in a large frying pan, add the tail meat and chopped artichoke hearts, and cook for 2—3 minutes, turning until golden. Transfer with a slotted spoon to a plate and keep them warm by standing over a pan of simmering water.
Add the wine to the pan, stir, then boil hard for 2 minutes. Reduce the heat and simmer for 4—5 minutes until reduced by about half.
Stir in the crème fraîche, season with salt, pepper and nutmeg, stir the head meat, liver and roes into the pan. Let the sauce bubble for 3—4 minutes until slightly thickened, then briskly whisk in the remaining butter.
Pile the lobster meat and artichokes into the cleaned shells, then pour the sauce over and sprinkle with chervil or parsley. Serve with wedges of lemon and a crisp green salad. This is a rich dish, so nothing else is needed.