Unfortunately I only ate from reputable shops here, never cooked myself. It is also very hard to prepare by yourself with raw materials. Small intestines of lamb is tightly coiled around lamb fat and cooked above hot coal or wood fire. Roasted bits are then cut into small pieces and cooked further on a hot plate, a lot of thyme and preferably diced tomatoes and some other spices are added. I don't know where you live but you may find packed frozen kokorec in small quantities in supermarkets which is ready to be cooked on a pan.