To make the first marinade, put all the ingredients into a large bowl, season with salt, and mix well.
Add the meat, coat evenly, then cover and allow to marinate in the refrigerator for about 2 hours.
Mix the yoghurt with all the ingredients for the second marinade in a large bowl or shallow dish.
Remove the meat from the first marinade. Using a knife scrape off any excess moisture from the first marinade and add the meat to the second marinade. Cover and allow to marinate in the refrigerator for a further 3 hours.
Prepare a moderately hot charcoal grill or preheat the oven to 190°C / 375”F / Gas Mark 5.
Thread the meat onto several metal skewers and roast over the grill or in the oven for about 15 minutes, or until the meat is cooked.
Remove the skewers from the heat and hang up to drain any excess moisture. Put the skewers into a dish and baste with the melted butter, then roast for a further 3-4 minutes. Serve hot.