1. Make incisions in a 2.25 kg leg of lamb and insert a quarter clove of garlic in each incision.
2. Combine 2 crushed cloves of garlic and rosemary, 200 ml Dijon mustard, 200 ml buttermilk, 50 ml oil and seasoning, spread it over the leg and leave for 8 hours.
3. Season the meat and place in a roasting tray, fat side uppermost. Coat with the dripping and place in the oven at 220°C. Reduce the temperature to 180°C after 20 minutes, allowing a total time of 1 1/2 hours and basting at regular intervals.
4. When cooked, remove the meat from the tray and stand it on a wire grid for 20 minutes. Any juices collected should be used in making the gravy.
5. Swill the pan with 500 ml brown stock and simmer gently for a few minutes. Strain through a fine strainer into a pan, reboil, skim all traces of fat and season to taste.
6. Carve across the grain of the joint, allowing one thick or two thin slices per portion. Arrange overlapping on a flat dish.
7. Lightly coat with some of the gravy and serve the remainder in sauceboats.