Lamb heart belongs to the offal family, or organ meat, which includes, liver, kidney, intestines, spleen, and testicles, among others. These meats, considered inferior in many countries, are fully enjoyed in Italy and other parts of the world.
It used to be said that in cities like Rome, where there is still a lively tradition of enjoying these lesser meats, organ meats were a trickle down from the bountiful tables of noble families and the households of wealthy churchmen, when the poor got the lesser cuts.
The heart of an animal, in this case, the lamb, is a rather tough muscle. The older the animal, the more time it takes to cook the heart, so these are usually braised and cooked for long periods of time. Hearts of younger animals may often be grilled, roasted or sauteed.
Choose hearts that are fresh smelling, plump, and red, and avoid hearts with a brownish or grayish hue. Refrigerate, loosely wrapped for no more than a day or two. Before using, remove any excess fat and wash thoroughly.