Order the leg from your butcher ahead of time; the leg bone should be sawed off at the extremity of the shank, just above the knuckle joint, and the leg should be cut somewhat above the pelvic joint—more or less depending on the size desired—and boned as far as the joint (that is to say, the section of pelvic bone removed) but no more. Correct carving is impossible in the interfering presence of the pelvic bone, but a boned leg of lamb, whatever its other virtues, always suffers a loss of succulence that refined little forcemeats do nothing to redeem.
Preferences in degrees of doneness may legitimately vary from rare to pink (which means well done in France), but those who are nervous if flesh is not cooked until gray will never understand what a glorious thing roast lamb can be; count from 10 to 12 minutes per pound, depending on the degree of doneness (from 45 minutes to 1 hour and 10 minutes should encompass both extremes, size being taken into account) and from 15 minutes to ½ hour of relaxation in a warm place (the time necessary to eat the preceding course—the relaxation period should not be too brief, but it may be prolonged with no damage done).
If rosemary grows in abundance and if the leg of lamb is being spit roasted, shortly before unspitting it remove the dripping pan for a minute while holding a large bouquet of smoldering rosemary beneath the revolving joint . . .