Salt and freshly ground black pepper
Preheat oven to 100 degrees C. Place lamb in ovenproof dish. Rub olive oil and salt and pepper over. Grind over salt and pepper and insert some rosemary sprigs and garlic slivers if you wish into the flesh. Make slits with a sharp little knife in flesh. Cover with foil and roast for 12 hours. (ideal to cook overnight)
To make the dressing: Mix the ingredients in a bowl and use electric beater to blend well.
Again, I often use only the yoghurt and the mayonnaise, mustard and honey and it works just as well, cutting a bit of fat.
I prefer serving the dressing seperately.