Sauté the Aromatics
In a large pot, heat the coconut oil over medium heat. Add the lemongrass, galangal, kaffir lime leaves, and onion, and sauté for 2-3 minutes until fragrant.
Add Broth and Coconut Milk
Pour in the chicken broth and bring it to a gentle simmer. Stir in the coconut milk and continue simmering for about 5 minutes to let the flavors meld.
Cook the Chicken and Mushrooms
Add the sliced mushrooms and chicken to the pot. Let the soup simmer for 10 minutes, or until the chicken is cooked through and mushrooms are tender.
Season the Soup
Add the Thai red chilies, fish sauce, and lime juice. Adjust the seasoning to taste; the soup should have a balance of salty, sour, and creamy flavors. Remove lemongrass and lime leaves before serving, if desired.
Serve and Garnish
Ladle the soup into bowls and garnish with fresh cilantro and lime wedges. Serve hot and enjoy!