Bring the coconut milk to a boil over medium heat.

Add the chicken broth to the pot and stir to combine with the coconut milk. Add the galangal, lemongrass, kaffir lime leaves, chili peppers, culantro, and cilantro roots.

Add the sliced chicken breast and season with fish sauce and sugar.

Add the mushrooms last. Turn off the heat, then stir in the lime juice.