Trim all fat
from the lamb, place the lamb in baking dish. Combine garlic, rosemary,
soy sauce and mustard and spread over leg of lamb. Bake, covered, in a
preheated oven until cooked to your taste. Remove leg of lamb from dish
and carve. Pour or skim the fat from meat juices. Blend cornflour
(cornstarch) with a little water to form a smooth paste, and add to the
meat juices. Heat until thickened, stirring constantly to keep the gravy
smooth, and pour over slices of lamb.