"Dip in crusty bread or whatever else you have on hand. Easiest party food ever."
While there is an apparently infinite variety of cheese, the basic ingredients for any cheese are incredibly simple: milk, salt, microorganisms, and a coagulating agent. The first three probably have the most influence on the ultimate flavor of the cheese, but when cardoon thistles are used instead of rennet or acid to coagulate the milk, it can produce a unique style of cheese that is worth considering on its own.
What the Heck Is Rennet?
In order to make cheese from milk, it must be coagulated, either with acid—in the case of fresh, crumbly cheeses like chevre or paneer—or with rennet, an extract of stomach enzymes found in juvenile mammalian stomachs (here are step-by-step instructions).
Because there has always been a limited supply of fresh juvenile calf (or lamb or kid or what-have-you) stomachs, and because in recent times vegetarians are uncomfortable with animal extracts being used in cheese, alternative rennets have been used for many years. Currently, much of the rennet used in cheesemaking, especially in large industry, is microbial in origin; that is, it's made from genetically modified bacteria which produce chymosin (the active enzyme in rennet) without any animals actually needing to be eviscerated. A win for everyone! (Purists claim this changes the taste or texture of the cheese, but that's pretty debatable.)
But, more interestingly for cheese lovers, the cardoon thistle, a relative of the artichoke and a current leading prospect for new, cool, indie vegetable of the next couple years, actually produces a close analogue of chymosin. Shepherds and cheesemakers in Spain and Portugal in the middle of the last millennium might not have known that, but someone figured out that if they stirred milk with the heads of the plant, the milk would coagulate and could be made into cheese. Thus were born some of the coolest, weirdest traditional cheeses in the world.
Like Cold Fondue
Cheeses made with thistle rennet tend to become extremely soft, even runny as they age, while at the same time developing a thick, leathery rind—they are essentially self-contained, no-prep-needed fondue. They also tend to be somewhat pungent (although they're no Epoisses or anything, so don't be too scared) and to have a pleasant vegetal bitterness, which I like to think comes from the thistle preparation. The coolest way to serve them is to buy a ripe wheel, let it come to room temperature, and cut off the top like a lid. Dip in crusty bread or whatever else you have on hand. Easiest party food ever.
The most common variety in the U.S. seems to be Torta la Serena, which I sold at Cowgirl Creamery, and which is easy to find but is sometimes mistreated at Whole Foods cheese counters. Torta del Casar is reputed to be wonderful, although I myself have not tried it.
Portugal produces even more of this style of cheese (although, as a dumb American, I find them harder to pronounce), including Serra da Estrela and the wonderfully pungent and diminutive Azeitão. Ask your local cheesemonger for any Portuguese or Spanish cheeses that they can get their hands on—they're certain to be interesting.
A note to the bovine-centric (or, like me, bovine-averse): Cardoon thistle is unsuitable for coagulating cow's milk, as it renders the final cheese unpalatably bitter, probably because of the different peptide sequence among different types of milk proteins. The cheeses discussed above are generally made from sheep's or goat's milk.