According to Celebrity Chef Sadaf Hussain, "My memory of mutton or lamb goes all the way back to my childhood to Eid-ul-Adha (Bakra- Eid). I remember using almost every part of mutton to make different delicacies - be it Korma, Razala, Paya or Biryani and others. While in the process of preparing these different dishes, I learnt how to make the mutton tender. One can use the kitchen hammer to break the muscle fibers or use knife to put cuts across the meat which helps it to cook faster and softer.
If you haven't known this already, the technique lies in how you slice the meat. For soft and tender slices, check the direction of the muscle fibers and cut across it, not with it, otherwise it will become chewy. This method also helps break up tough proteins, further helping meat to absorb tenderizing marinades more easily. So if you thought that slicing or cutting the meat does not matter much, it's time to give it a thought!
Chef Sadaf tells us to leave the meat in curd or papaya paste to tenderise the meat for at least 2-3 hours, and if you have enough time, leave it for about 6-7 hours. For making the prefect Kachi Gosht ki Biryani or Galouti Kebab, meat is left to marinade overnight. Another trick is to make use of curd, papaya, buttermilk or acidic fruits like lemon or kiwi with salt and pepper, which help in breaking down the solid fibers of meat. People generally use nutmeg as well, but it changes the flavour of the meat so you can avoid using it. The acids in a good marinade help to break down the collagen between the fiber muscles that hold the meat together. Once these fibers break down, that's when the meat becomes tender and ready to devour. Marinating not only makes the meat tender, but also adds moisture to it, further making it juicy.
One way to make mutton tender is to cook it slow. As per Chef Amit, braising or slow cooking the mutton for more than 3 hours on low temperature helps soften it. This method is followed in European style of cooking. Tough fibers, collagens and connective tissues will eventually break down, making it softer.
If you don't wish to marinade the mutton, salt it instead and let it sit for about an hour or two before you start cooking. This is one effective way to break the muscle fibers down without any hassle. Rinse off the excess salt and then start cooking.
Apart from these techniques, it is imperative to buy the right kind of meat. According to Chef Sadaf, "buying meat can be really tricky. When I am buying meat, I always look for pieces with clear hard and white fat. Freshly butchered meat is colourful and eye catchy as compared to old or frozen meat. I also look in to the fibers. If they are broken or loose, that basically means poor quality meat.