At Bā Hào, a bar in Bangkok’s Chinatown, we were smitten with the tan tan mian, a soup that featured chewy wheat noodles in a rich, spicy-sweet peanutty broth, finished with bits of ground pork, shiitake mushrooms and sesame seeds. Sichuan pepper add tongue-tingling flavor, while bok choy supplies color and crispness. It’s a muddle of a dish—a Thai riff on a Japanese dish that actually originated in China. We like the nubbiness of chunky peanut butter in the broth, but smooth is fine, too, if that’s what’s in the pantry. And any type of peanut butter—regular (such as Skippy or Jif) or natural (no added sweeteners or oil)—will work. For convenience, the soup can be made ahead and refrigerated in an airtight container for a few days. When ready to serve, reheat the soup while you cook the bok choy and noodles, portion and serve.