If using wooden skewers, first soak them in water for 5 mins to stop them from burning under the
grill. Swap the lamb for chicken or pieces of firm tofu for a lower fat version and pack the pittas with plenty of salad.
Heat the grill to medium. Mix the yogurt and mint sauce together, then divide the mixture in half. Stir the cumin into one half of the yogurt mix, then pour over the diced lamb. Mix thoroughly to coat and season well.
Thread the lamb onto 4 skewers, alternating with pieces of onion, then arrange on the wire rack of a grilling tray. Grill the kebabs for 3-4 mins on each side, until the lamb is cooked through and the onion is beginning to brown. Warm the pittas in a toaster for 1-2 mins and split open. Stuff the pittas with lamb, onion and lettuce, drizzling over the remaining minty yogurt to serve.