Eventually, it is said, every good idea reaches its logical extreme. If it's true that the Lascaux cave paintings held the seed of the Sistine Chapel and the abacus was merely the Internet 0.1, then mutton skewers sold on the streets of Beijing were the precursor to the ultimate Beijing barbecue - a entire roasted leg of mutton.

At Tanhua Kao Yangtui, a nondescript restaurant in a hutong near Yonghegong, or Lama Temple, the beer's cold, the conversation is loud and the tables are laden with meat. Variety is not a specialty.

Here, it's all about the roasted mutton leg, an enormous and succulent joint barbecued at the table over a bed of hot embers pulled from a bucket of burning coals. Joints start at about 1 kilogram, which feeds about three people.

Rather than cook the whole joint before eating, you receive a raw joint and, using a foot-long knife and fork, cut slices off the surface as it cooks, so every morsel is browned and crispy.

Once you clear off the top of your roast, you just turn it over and eat the other side while it continues cooking. When the joint eventually begins to fall off its skewer, the staff will take it away and return with the rest in bite-size grilled pieces.

Finishing a whole leg of mutton takes at least 80 minutes, so it's definitely a meal for an occasion, if eating a whole leg of mutton isn't occasion enough. Go hungry and prepare to wash down your meat with bottle upon bottle of Yanjing beer.

The mutton comes with a few sauces and a spicy seasoning, and the restaurant also serves cold dishes and kebabs. The mantou (steamed bread) kebab goes especially well with the mutton, while the cold wood ear mushrooms in wasabi sauce make an intense, tasty appetizer.

A roast leg of mutton may not be a small step for meat, but it's a giant leap for kebabs.