Take a large bowl and add the yoghurt along with the grated onions, garlic, cumin, coriander, turmeric and season with the salt and pepper. Mix well and then add the minced lamb. Mix thoroughly for almost 2 minutes and then add the fresh coriander. If you want to refrigerate overnight, then lightly brush the mixture with olive oil and cover with plastic wrap, otherwise skip step No. 3 and form the kefte as described in step No. 4.