Perhaps they are not quite so common now as they were a decade ago, before the Olympics and the city's efforts at beautification, but the roads still sport pushcarts and makeshift stalls, and their owners continue to ply their trade.
Walk along any major thoroughfare, and you'll pass vendors selling baked sweet potatoes out of big metal drums pulled on pedal bikes. Turn down a side street, and you'll find hawkers with bing tang hu lu, bamboo skewers of candied hawthorn berries sold out of pushcarts with glass cases. Stand at a street corner in an older corner of the city, and you might catch the scent of smoke and charring sugar that marks a stall selling tang chao li zi, sweet roasted chestnuts.
The chestnut sellers come out in late autumn, after the trees have shed their leaves, becoming part of the landscape in winter. Sometimes these stalls evolve to sell a variety of snacks, and then remain as permanent fixtures.
There is one such stall near my office, a small space with a counter that opens onto the street. It sells all kinds of snacking nuts by weight: whole almonds and walnuts, peanuts and sunflower seeds in the shell. The draw, however, is still the roasted chestnuts.
The chestnuts are roasted whole, tumbled with hot charcoal in big metal pans. Even when it is bitterly cold outside, queues form when a new batch is being prepared.
The vendors stir the nuts, testing them as their shells begin to turn dark. When they are judged to be ready, the vendors pour them into big mesh baskets, and weighed them out into sacks fashioned from coarse brown paper.
Shelling these chestnuts is a two-handed process, so there's no eating them out of the bag on the street. Instead, I cradle the paper sack in my hands, warming my fingers in the chilly air. Returning indoors, I place the bag on a flat surface and set to work.
Chinese chestnuts are smaller than the European varieties, with a fine, papery skin and creamy yellow flesh. The shells are thin, easily cracked by breaking open their flat sides with the edge of a thumbnail. There's a pleasure to the process, like that of eating boiled shrimp or picking over a whole crab, each chestnut its own reward.
The last time I stopped at a roast chestnut stand, I bought more chestnuts than I planned to eat and shelled the rest for use in culinary experiments. My first thought was Mont Blanc, the classic French dessert: a meringue base topped with sweet chestnut puree, decorated generously with whipped cream. Much of its charm lies in effective presentation, however, and I lack the equipment necessary to form the chestnut puree into fine threads.
Instead, I opted for a different preparation. After turning my roasted chestnuts into sweet puree, I combined them with custard and folded in gelatin and whipped cream, spooning the mixture into decorative glasses. The French call this dessert crème bavaroise (or just bavarois), and it's a lovely finish to a holiday meal.
In this city of street vendors, it might even become part of my culinary landscape.
If you're not in a place where roasted chestnuts in the shell are readily available for purchase, don't drive yourself mad trying to track down fresh chestnuts to roast from scratch. Vacuum-packed, jarred, or tinned chestnuts will all work just fine - just make sure they don't have any sugar added.
(Makes a lot. It's very rich, so a little goes a long way.)
Take seven ounces of shelled chestnuts (about eight ounces in the shell) and place them in a small saucepan with two tablespoons sugar and enough water to cover. Cook, stirring frequently, over very low heat, until the chestnuts start to soften and break up easily when pressed with a spoon. (Keep an eye on them. Chestnuts are like beans, and will burn on the bottom if they catch.) Set the mixture aside to cool.
When the chestnuts have cooled to lukewarm, use a stick blender or food processor to blend them into a smooth puree. Measure out eight ounces of chestnut puree, and set aside. (Any extra is nice on toast.)
In a small bowl, cover two sheets of gelatin (four grams) with a quarter-cup of warm milk.
Separate four egg yolks into a heatproof bowl. (Save the whites for baking.)
In another saucepan, combine half a cup of milk with two tablespoons sugar and half a teaspoon of vanilla. (Optional extra: a tablespoon of brandy or rum.) Heat, stirring frequently, until the sugar dissolves.
Carefully whisk the hot milk mixture into the egg yolks, beating well to incorporate. Transfer the mixture back to the saucepan. Add a fat pinch of salt. Cook over low heat, whisking steadily, until the mixture thickens and the whisk starts to form trails. Remove from heat, and whisk in the gelatin mixture. Stir in the chestnut puree. Set aside to cool.
Beat three-quarters of a cup of heavy cream until it forms stiff peaks. Gently fold into the chestnut custard.
Spoon the mixture into glasses, and chill in the fridge overnight. Decorate with whipped cream (and marrons glaces, if you like) before serving.