Pat dry the leg of lamb with kitchen towel. Season really well with salt, pepper and a drizzle of oil.
Heat a large cast iron skillet on a medium heat. Sear the meat on all sides until nicely coloured - this will take around 10 minutes. If it starts to catch, add a splash of water to stop it from burning.
In the meantime, chop the carrots, parsnips, red onions, and celery. Place them in a roasting tin.
Once all the veggies are in the roasting tin, peel and chop the garlic, remove the rosemary leaves from the stalk and add both into a pestle and mortar. Bash together until a paste forms. Next, add 1 tsp of honey, 2-3 tablespoons of oil, and a pinch of salt and pepper. Bring it all together in the pestle and mortar.
Pre heat the oven to fan 140
Once the lamb is nicely coloured on all sides, place it on top of the veggies. Carefully cut some incisions across the top of the meat. This will help the garlic and rosemary marinade penetrate the meat.
Rub the garlic and rosemary marinade into the incisions until the meat is covered.
The skillet that you have seared your lamb in will have so much flavour. Add two lamb stocks along with 400ml of water to the skillet and deglaze. Once the stock comes to a bubble, remove from the heat and pour it into the roasting tin with the lamb and veggies. Be careful not to pour it over the top of the lamb.
Finely cover the roasting tin with foil and slow roast in the oven for 8 hours. Check after around 6 hours - you may need to add some more water so that the veggies don't burn.
Notes
This slow roasted leg of lamb goes incredible with mustard mash, roasted and steamed vegetables.