1. Preheat the oven to 150C (130C fan-forced).
2. Using a sharp paring knife,make deep incisions all over the lamb leg:this will help the flavours of the marinade get into the leg.
3. Put the butter into a small bowl,add the other marinade ingredients and mix thoroughly until a paste is formed. Use your hands to rub this paste all over the lamb leg,pushing it into the cuts in the leg as much as you can.
4. Place the lamb leg on a cake rack in a roasting tray and roast for four hours,basting the lamb with its juices every 30 minutes or so. Cover with foil after three hours if the meat is browning too much.
5. Once cooked,remove the lamb from the oven,cover with foil and rest for at least 30 minutes.
6. Cut lamb into slices. On four plates,put a spoonful of eggplant chermoula (recipe below),then top with lamb slices,drizzle with extra virgin olive oil,squeeze over some fresh lemon juice and give a little sprinkle of salt and a good grind of fresh pepper. Serve immediately.
To make the eggplant chermoula
1. Season the eggplant with salt. Heat olive oil in a saucepan over medium heat (you'll need enough oil for about 1cm depth) and fry eggplant in batches until golden (about 5 minutes),turning regularly. Remove with a slotted spoon. Repeat until all eggplant is cooked. Drain any remaining oil into a heat-proof bowl.
2. Return the pan to medium heat with 1 tbsp of fresh oil,add the garlic,cumin and paprika and stir,then add the tomatoes. Cook for another 8 to 10 minutes,then add the vinegar and honey.
3. Cook for a further 2 minutes or until reduced,then add the cooked eggplant. Stir through,remove the pan from the heat and serve with the lamb.
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