1.Blend or process yoghurt, oil, chilli, garlic, ginger and spices until smooth. Combine yoghurt mixture in a large shallow dish with lamb. Cover; refrigerate 2 hours or overnight.
2.Place lamb in a deep disposable baking dish; cook in a covered barbecue, using indirect heat, following manufacturer’s instructions, about 45 minutes or until cooked as desired. Remove from barbecue; cover with foil, rest 15 minutes.
3.Meanwhile, make date and pistachio couscous. Bring consommé to the boil in a medium saucepan; remove from heat, add couscous. Cover; stand about 5 minutes or until liquid is absorbed, fluffing with fork occasionally. Stir in remaining ingredients; season to taste.
4.Serve lamb with couscous.
If you can’t find fresh dates, use ½ cup (70g) coarsely chopped seeded dried dates. The lamb can be cooked in the oven, if you prefer. Preheat oven to 180°C/350°F and roast, uncovered, for about 45 minutes. Ask the butcher to butterfly the leg of lamb for you.