There are several ways in which we can go about thawing a leg of lamb and several ways in which we should not go about doing it. There is also the option of simply cooking the leg of lamb from frozen. Let us therefore examine this conundrum in more detail.
First of all the don'ts, as we neither wish to waste our beautiful and probably expensive leg of lamb nor perhaps make it unfit for human consumption! We must never therefore leave it simply lying on a work surface or counter top to defrost, either covered or uncovered. This can allow harmful bacteria to develop in the flesh, something we obviously do not want to happen. In a slightly different sense, nor should we consider thawing our leg of a lamb in the microwave oven. Microwaves destroy the texture and taste of most foods but especially meat. We therefore wish to keep our lamb in pristine condition for the best possible eating experience.
The best way to defrost our leg of lamb is in the refrigerator. We should remove, or at least unseal, any packaging and place it on some form of tray or baking sheet with raised edges to collect the water and blood as the leg defrosts. We must also ensure that we place the lamb on the very bottom shelf of the refrigerator so that any juices which do drip will not contaminate the other food we are likely to have stored there. This defrosting process will take a minimum of twenty-four hours but may take up to thirty-six in extreme cases, dependant obviously upon the size of the leg.
In order to speed up the process, we may wish to place our leg of lamb, still sealed in its packaging, in the sink, fill the sink with cold water and leave it for twelve hours or overnight. This method should however only be used in emergencies and the previous option is the desirable one.
If we so choose, however, it is perfectly possible to cook our leg of lamb from frozen, without waiting for it to defrost. Naturally, this will considerably extend the required cooking time but may be an option we are forced to consider if, for example, we "forget" to remove the lamb from the freezer far enough in advance. We would be required in this case to cook the leg for around fifty minutes per pound at a reduced oven temperature of 300F/150C. This will ensure that the meat is evenly cooked as it thaws in the oven and does not burn and dry out on the outside while remaining raw or under-cooked on the inside.
It then remains simply a matter of breaking open the mint sauce and enjoying our delicious leg of lamb to the full.