This is a muscular organ that works hard, so it's very tough when uncooked. Much like beef heart, you have two options when cooking it. Either slice it very thin and cook it quickly, as they do in Korean barbecue. Or cook it low and slow, in a saucepan or in your slow cooker. I like the second method better because it results in meat that literally melts when you put it in your mouth. So wonderfully tender! And despite owning a slow cooker, I prefer to cook it on the stovetop in water. This is mostly because then I get a wonderful bonus - rich, flavorful homemade beef broth!