Belinda Leong's kouign-amann, a Breton cake made of layers of butter and sugar-slathered pastry dough baked up into a delicate celebration of caramelization and custard, had potential to be this city's version of the cronut. When she opened b. patisserie in February, the kouign-amann routinely disappeared in a few hours, but she got the amount on lock before huge lines had a chance to form and you should be able to find one there for most of the day. And now, you can even find at least two additional kouign-related products.
Leong sometimes sells filled kouign-amanns; she started with a giant "bleeding heart" one with cassis, blackberry, pomegranate, and raspberries shortly after opening for Valentine's Day. She currently offers a blueberry version for summer.
Perhaps more dangerous is the bag of kouign-amann "ends" that are bagged and sold at the counter. They capture the crispiest and most caramelized element of the item, which triggers all kinds of pleasure centers in the brain. One advantage of these over the actual kouign-amann is that the ends maintain their texture for longer, it's far too easy to take down a whole bunch of them in one swoop so you'll probably never know this for sure.