Make the herb sauce by pouring half the lime juice and half the olive oil into a liquidiser. Switch on the machine and add all the other ingredients till they are finely chopped and are well amalgamated with the oil and juice. Turn off the liquidiser and check the consistency of the sauce – it needs to be thick but easily pourable, so if necessary start the machine again and add more juice and oil. Chill the sauce thoroughly before serving.
To roast the lamb, pre-heat the oven to its maximum temperature and meanwhile, in a large hot frying pan, seal the leg all over. Once sealed, season with salt and pepper. Put the cloves of garlic, unpeeled, in a roasting tin, place the lamb on top of them and pop into the oven with nothing else at all. After 30 minutes, take out the lamb, turn it over, place it back on the garlic and lay the anchovy fillets on top of the leg. Pour the water around it and return to the oven (I know the oven’s a bit smoky, but don’t worry about that). Cook for another 20 minutes.
When the time is up, lift the roasting tin from the oven and whisk the juices in with a fork, making sure to scrape any bits off the side – if the liquid has reduced to almost nothing, simply add another cup or two of water. Remove the garlic cloves from under the meat and keep them warm. Return the meat in the tin to the still-hot oven and switch the oven off. Leave the meat inside for another 15 to 20 minutes.
To serve, put the meat on a warm serving dish with the roasted whole cloves of garlic. Carefully pour all the liquid from the roasting tin into a saucepan and bubble it up on the stove. Whisk in the butter little by little till you have a thin creamy sauce. Strain through a fine sieve over the meat. Serve the chilled herb sauce separately, whisking it with a fork just before bringing it to the table.
© 1988 Keith Floyd estate. All rights reserved.