French Roast Leg of Lamb, with Gratin Dauphinois and Green Beans

Ingredients

• 2.5kg leg of lamb, bone in (Centre Cut Gigot)
• 6 cloves garlic, crushed
• 2 large sprigs of fresh rosemary
• 2 to 3 tbsp olive oil
• Freshly ground salt and pepper, to season
• Dauphinoise Potatoes:
• 1kg desiree potatoes
• 1 shallot, chopped
• 1 clove garlic, peeled and halved
• 300ml whole milk
• 284ml carton double cream
• 25g parmesan, freshly grated
• 2 to 4 sprigs of fresh thyme
• Pinch of freshly grated nutmeg
• Freshly ground salt and pepper, to season
• Knob of butter
• Gravy:
• Juices and fat from the roasting pan
• Approximately 1 cup red wine
• 1 tbsp flour
• 1 tbsp water
• To Serve:
• Green beans, if desired

Method

1. The night before you intend to roast the lamb:
2. Cut 1 inch slits in the leg of lamb and fill these with crushed garlic and rosemary sprigs. Place the lamb onto a roasting rack, within a roasting tin, cover lightly with cling film (or similar) and pop into the fridge. The flavours will then infuse into the lamb overnight.
3. In advance, on the day of roasting the lamb:
4. Remove the lamb from the fridge 2 to 3 hours before you plan to start cooking it, allowing it to warm up to room temperature.
5. At the time of cooking:
6. Preheat the oven to 230 degrees C / 450 F / Gas Mark 8.
7. Drizzle the lamb with olive oil, making sure all of it is covered (a pastry brush can be helpful for this), then sprinkle it with salt and pepper.
8. Pop the roasting tin into the oven and roast for 15 minutes, then lower the temperature of the oven to 150 degrees C / 300 F / Gas Mark 2. Continue to roast the lamb at this new temperature for a further 2 to 3 hours for medium doneness. You will know the lamb is cooked to your liking when the internal temperature reaches 65 to 70 degrees C when a meat thermometer is inserted into the thickest part of the meat. [NB: For medium-rare you are aiming for 60 to 65 degrees C and for medium-well you are aiming for 70 degrees C.]
9. Whilst the lamb is cooking, prepare and cook the dauphinois gratin (this will take about 90 minutes in total).
10. Take a roasting dish (approximately 18 x 28 cm) and rub the butter all over it to make sure it is thoroughly greased. Peel the potatoes and slice them thinly (e.g. 3mm thickness), laying the slices on a clean tea towel and patting them dry. Keep the potato slices covered with a tea towel whilst you prepare the other ingredients.
11. Take a saucepan, pour in the milk and cream, then add the garlic, 2 sprigs of the thyme and the shallot. Slowly heat the mixture, stirring continually, until it almost reaches boiling point and you start to see bubbles around the edge of the pan; at this point, remove the pan from the heat. Pour the liquid through a sieve into a large jug, add in the nutmeg, stir and keep warm.
12. Layer half of the potato slices into the roasting dish, slightly overlapping them, then sprinkling with salt and pepper to season. Now, pour half of the hot milk and cream mixture over the potatoes, then layer the rest of the potatoes on the top before pouring over the remainder of the liquid. Finally, scatter the parmesan over the top and bake for about an hour (i.e. in the oven with the lamb) until the potatoes are golden and tender. Once ready, remove from the oven and keep warm until ready to serve.
13. Once the lamb reaches the desired temperature, remove from the roasting tin and leave to rest on a warm plate for 10 to 15 minutes, covered loosely with tin foil
14. Use this resting time to cook the gravy and green beans (i.e. boil for 3 to 5 minutes and then drain).
15. To make the gravy, pop the juices and fat from the bottom of the roasting pan into a saucepan with some red wine, to make up 1 cup of liquid. Now, mix 1 tbsp flour with 1 tbsp water until you have a smooth paste, then stir this into the liquid in the pan and simmer over a low heat until thickened.
16. Once everything is ready, carve the lamb and serve with the potatoes (sprinkled with a few fresh thyme leaves from the remaining sprigs), beans and gravy on warm plates.