Cong you bing (葱油饼, literally scallion oil flatbread) are the flaky, layered, scallion-studded flatbreads that appear at breakfast stalls across northern China and Taiwan — one of the most beloved and technically elegant preparations of Chinese dough cookery. The flakiness is achieved through a lamination technique: hot water dough is rolled thin, brushed with an oil paste (sometimes using lard, sometimes using oil mixed with flour), scattered with chopped scallion and salt, rolled up into a cylinder, coiled into a snail shape, then rolled flat again — the rolling-and-coiling creates dozens of thin layers of dough-and-fat that separate during frying into flaky, slightly crisp, aromatic layers.
The hot water dough: 200g plain flour + 100ml just-boiled water + pinch of salt. Knead 8 minutes until smooth. Rest 30 minutes covered. Hot water dough produces a more pliable dough that is easier to roll very thin without tearing. The oil paste: 30g flour + 30ml very hot oil + 1/2 tsp salt. Mix until combined — a thick paste. This is brushed across the rolled-out dough to create the fat layer for lamination. The lamination: Roll the dough into a very thin rectangle. Brush the entire surface with the oil paste. Scatter generously with finely chopped scallion and a little more salt. Roll the dough tightly from one end (like a Swiss roll). Coil the resulting cylinder into a snail shape. Tuck the end under. Gently press flat with your palm. Roll into a circle (15-20cm). The fry: Heat 2-3 tbsp oil in a skillet over medium heat. Fry the pancake 2-3 minutes on each side until golden and slightly blistered. The internal temperature should be high enough to cook the dough through — press gently: it should feel firm throughout.
Rolling the coiled dough too aggressively: Over-rolling destroys the laminated layers. Roll gently, allowing the layers to remain intact. Insufficient oil in the frying: The pancake should be shallow-frying in enough oil to develop a proper golden crust.
Fuchsia Dunlop, Every Grain of Rice (2012); Eileen Yin-Fei Lo, Mastering the Art of Chinese Cooking (2009)