While this soup can be made on the stovetop in under an hour, it benefits from a longer spell in the slow cooker. The lemongrass and lime leaves infuse more flavor into the broth and the tender, moist chicken thighs. —Food52
On a cutting board, using the side of a chef’s knife, lightly smash lemongrass. Combine lemongrass, broth, fish sauce, sugar, galangal, lime leaves, shallot, chiles, chicken, and mushrooms in the slow cooker. Cover and cook on high until chicken is cooked through, about 2 1/2 hours (or on low for 5 hours).
Add coconut milk and carrot, and cook on high 30 minutes longer (or on low for 1 hour). Stir in lime juice, cilantro, basil, and scallion. Top with cilantro and basil, and serve with chili oil sauce.
Tip: Chili oil sauce—a mixture of ground dried chiles, soybean oil, garlic, and sesame oil—is sold in Asian markets and even many supermarkets. It can be used in any recipe that calls for red-pepper flakes.