[Lamb Melts; Tilli (Hindi)]
These are usually labeled "Lamb Melts" in the markets to avoid the rather anatomical "Spleen". It is most used in North African cooking, but also anywhere sheep and goat are feature meats. The larger of the two photo specimens (front and back) was 6-1/2 inches long, 4 inches wide and 1 inch thick, weighing 5-1/2 ounces.
More on Lamb Innards.
Spleens are most commonly combined with kidneys, livers, lungs and other sheep innards in recipes, but in Morocco they are often split open and stuffed. In favor it's similar to liver but milder, but its texture is is chewy rather than soft and crumbly like liver.
Buying: These can be found labled "Lamb Melts" in markets serving Turkish, Armenian, Middle Eastern and North African, and any other communites that are big on sheep and goat.
Prep: Some recipes call for peeling away the skin and tendons, but spleens sold in markets here are cleaned and ready to go. There is an outer membrane which you could remove if you really want to but that's difficult to do.
Cooking: These need to be simmered for some time. At 10 minutes they have the texture of a very soft, springy rubber and cannot be chewed. At 1-1/4 hour they're still a little chewy, but quite edible.
Recipes: If you search for recipes on the Internet, search for "Lamb Spleen". "Lamb Melts" will get you only hundreds of descriptions of dishes where "the lamb melts in your mouth" and no recipes.
Health & Nutrition: Spleens are very high in dietary iron.