There are delicious roujiamo (Chinese sandwiches of long-braised meat, pickled veg, crunchy bits) to be had at Mama Wang's, a stall at Archway's market. They also go to other markets (Catford, this weekend, apparently) and they are well worth checking out. Their pork and lamb are delicious, cooked for nine hours til they're falling apart (maybe, actually, falling apart too much, I like my meat a little more toothsome) in an array of spices and more-ish sauce. All the accoutrements are top-notch, too. The sandwich is on an English muffin rather than Chinese flatbread, but I'm not sure it makes much of a difference. In fact, the muffin soaks up a lot of sauce, which I'm not sure a flatbread would be able to do. Don't wear new or fancy clothes - the sauce will get everywhere.