A common sight in Jakarta are the many food stalls displaying banners featuring images of catfish and chickens that are set up on sidewalks, enlivening the capital city’s frantic streets every evening.

While famous for their pecel lele (fried catfish), the vendors, who typically come from Lamongan, East Java, also serve pecel ayam (traditional fried chicken) and soto ayam (chicken soup served with noodles). The dishes are common favorites among Jakartans, with customers typically paying less than Rp 30,000 (US$2.14) per portion.

Customers have probably also noticed that these stalls display similar banners, even if they have no relation to each other. The banners, which are usually placed at the front and two sides of each stall, always consist of a white background, with striking-colored lettering...