Prepare the marinade by grinding the coriander, cumin, cloves, cinnamon, peppercorns, fenugreek and fennel in a spice grinder or mortar and pestle. Process the chiles with the garlic, onion and ginger to form a paste. Place the meat into a container. Pour the marinade over the meat and marinate, refrigerated, for at least three hours or overnight. Remove the lamb from the marinade and drain. Combine the curry paste with the vinegar. Rub the paste onto the meat.