- Preheat the oven to 220 °C (450 °F).
- In a bowl, combine the garlic, breadcrumbs, egg, mustard, rosemary, thyme and olive oil. Season with salt and pepper. Untie the leg while maintaining its shape. Trimmed off the fat and place on a baking sheet. Place the bones around the meat. Sprinkle with the breadcrumbs and press on the leg to make a crust. Add 750 ml (3 cups) of water around the lamb. Bake for 20 minutes. Reduce the oven’s temperature to 190 °C (375 °F) and bake for about 1 hour and 10 minutes for medium rare. Cover the roast with aluminum foil, if necessary. If you have a meat thermometer, the internal temperature of the roast should reach 55 °C (132 °F) for medium rare. Add the remaining water during cooking. Remove the lamb from the baking sheet. Keep warm. Pour the contents of the baking sheet in a saucepan.
- Add the consommé, port wine and a sprig of rosemary. Simmer for 5 minutes. Season with salt and pepper and strain the cooking juices through a sieve. Thinly slice the lamb and serve with the sauce. Garnish with rosemary sprigs.