The aromatic vegetables in the broth create a light yet distinct flavor of classic noodle bowls. Adding the lime juice, fish sauce and shrimp at the end keeps them from overcooking and their flavors from becoming diluted. If you have it, drizzle toasted sesame oil on top of this slow-cooker shrimp dish for nutty flair. For the prettiest appearance, use whole basil and cilantro leaves, instead of chopping them. Look for packaged lemongrass stalks near the plastic clamshells of herbs in the produce section of your supermarket.