Lamb fillet is a very lean, tender cut of lamb which requires virtually no preparation and cooks very quickly. Choose from Welsh lamb loin fillet or New Zealand lamb loin fillet at Waitrose. When acquire lamb loin fillet for roasting you may cut fillet into small pieces with a knife to provide smooth flavor. Loin fillet is ideal for roasting, pan-frying, griddling or stir-frying. For stir frying, cut the lamb into 1cm strips, cutting across the grain to prevent shrinkage and help tenderize the meat. To grill fillet slices, brush with a little olive oil to keep it moist during cooking and then cook under a preheated grill for 3-5 minutes on each side. To stir fry loin fillet, heat 1 tbsp oil in a frying pan and stir fry strips of meat until browned, add any vegetables and flavorings and cook for another 2 minutes. To pan-fry slices of loin fillet heat 1 tbsp oil in a frying pan add the lamb fillet and seal on both sides, this helps to keep the meat moist during the cooking time. Turn the heat down for the remaining cooking time and cook for 2-4 minutes on each side.