Lvdagun Rolling Donkey

Lvdagun belongs to the old粘食 (glutinous snacks) of Beijing and is listed among the 老北京小吃十三绝, the city's thirteen famous street snacks. Its other, more literal name is 豆面糕, soybean-flour cake. The vivid name 驴打滚 — 'a donkey rolling about' — is generally explained as a picture rather than a person: when the finished roll is tumbled through the toasted soybean flour, the flour flies up and coats it like the cloud of dust kicked up by a donkey rolling in the dirt of the open country, and the name stuck. Two folk tales are commonly attached — one crediting the Eastern Han general Ma Wu (马武), who is said to have seen a pack donkey rolling in yellow earth, another setting the accident in the Qing palace kitchen of the Empress Dowager Cixi — but both are popular legend, not documented history, and reference accounts treat the dust-rolling image as the real source of the name.

A piece is soft, dense, and stickily chewy, clinging just slightly to the teeth in the way of all good glutinous-rice sweets, never hard or dry. The outer coat of toasted soybean flour is the first thing you taste — dry, warm, nutty, faintly toasty — and then the dough gives way to a band of sweet red-bean paste running through the middle, smooth and a little earthy. The soybean dust also keeps the sticky surface from gluing to the fingers. Eaten the day it is made it is supple and fragrant; left overnight the glutinous dough firms and turns tough and rubbery, and the soybean flour goes stale and flat, which is why it is sold and eaten fresh.

The chew comes from glutinous starch. Glutinous millet and glutinous rice are almost pure amylopectin — the highly branched starch — with little or no amylose, so when the flour is hydrated and steamed the granules swell and the paste sets into a dense, elastic, sticky mass that stays soft and does not crumble. The same chemistry explains why it goes hard overnight: as it cools the amylopectin chains slowly re-associate (starch retrogradation), squeezing out water and turning the soft dough firm and rubbery, so the snack is best fresh. The soybean flour is dry-toasted first: heating develops a roasted, nutty aroma through Maillard reactions between the bean's proteins and sugars, and the dry powder both flavors the roll and, by coating its surface, keeps the very sticky dough from adhering to hands and board. The red-bean paste, cooked down with sugar, supplies the sweet, smooth core.