Jian bing guo zi (煎饼果子, literally fried cake with the crispy thing) is the most iconic Beijing breakfast street food — a thin mung bean or wheat flour crepe cooked on a flat, circular griddle (鏊子, ao zi), topped with a beaten egg spread across its surface, scattered with sesame seeds, chopped coriander, and scallion, spread with sweet bean sauce (tian mian jiang) and chilli sauce, then wrapped around a shattering-crispy fried wonton wrapper or fried crullers (you tiao). The combination of soft crepe, runny egg, savoury sauces, and the exploding crunch of the fried wrapper is one of the great textural sequences in Chinese street food.
The batter: 100g mung bean flour (lu dou mian, 绿豆面) + 50g wheat flour + water to a thin, pourable consistency. The mung bean flour produces the characteristic slightly yellowish colour and earthy flavour. In modern versions, 100% wheat flour batter is also used. The griddle: A flat, slightly convex circular griddle (approximately 50cm diameter) heated over a flame. Lightly oil the surface. The cooking sequence: Pour the batter onto the griddle. Spread into a thin circle using a T-shaped wooden spreader (similar to a crepe spreader). When the top surface begins to set (30-45 seconds), crack an egg (or two) onto the crepe. Spread the egg across the surface with the back of the spreader. Sprinkle with sesame seeds, chopped coriander, scallion, and dried chilli flakes. When the egg is set (30 seconds more), spread tian mian jiang and chilli sauce across the surface. Place a fried wonton wrapper (bao cui, 薄脆) or broken you tiao in the center. Fold the crepe around the filling — first one side, then the other, then the top and bottom.
Fuchsia Dunlop, Every Grain of Rice (2012)