The secret to making delicious pho is layering flavors to create a rich and fragrant broth. Thankfully, most of the ingredients used by Vietnamese cooks are readily available at Asian markets. Black cardamom, a seedpod about the size of an olive pit, gives pho its savory depth. The spice smells of menthol and smoke, and it imparts a surprisingly earthy aroma. Another pho signature spice, star anise, is a brown eight-pointed pod that lends a hint of licorice to the broth. When buying either spice, choose a store that has a high turnover of spices, to ensure freshness. Umami is also a defining flavor of pho, and two ingredients—fish sauce and dried scallops—help create that savory depth. When buying fish sauce for pho, look for a Vietnamese-style sauce, such as the Three Crabs brand, which is delicately flavored and has a translucent reddish tea color. A few tablespoons added toward the end of the brewing process give the broth a funky richness. Dried scallops, meanwhile, are a natural alternative to MSG, infusing the soup with a saline dimension. Find them at Chinese markets, sold by the bag in the refrigerator case. For use in pho it's all right to buy the smallest, less-expensive scallops. Linguine-width rice noodles can be purchased in the dry-goods section of an Asian market; we like Three Ladies brand from Vietnam. Good rice noodles are silky yet toothsome when rehydrated in water.