Trying to keep track of the best dim sum in town can sometimes feel like keeping up with a foodie soap opera — the best chefs are highly trained to craft the tiny dumplings, complex soups, and exotic delicacies, and therefore prone to being poached by competing restaurants. The hottest dim sum in town can go abruptly cold with the departure of a star chef. Despite the turmoil, there is one surefire way to distinguish the champs from the chumps: rice flour skins and noodles. The proper skin on a har gow, for example, is pretty tricky — it's got to be soft but not gooey, luscious but not too thick. On Saturdays and Sundays at Yangtze, the kitchen passes this litmus test with flying colors. The dumplings are perfect, the cheung fan is practically addictive, and everything else falls into place thereafter. All the staples — from cha siu bao to sticky rice to tofu skins — simply put regular brunch to shame. Plus, while Yangtze does a brisk business, its lobby doesn't suffer the same crush of people sometimes found at other popular dim sum destinations.