Start by heating your large pot over medium heat. Add a splash of oil if desired. Once the pot is warm, toss in the sliced lemongrass and fresh grated ginger. Sauté for about 2 minutes.
Next, add the sliced chicken breasts to the pot. Cook for about 5-7 minutes, stirring occasionally, until the chicken is no longer pink.
Pour in the quart of chicken stock and bring the mixture to a gentle simmer. Add the soy sauce, cayenne pepper, and sugar. Stir well to combine.
Once your broth is simmering, add the sliced mushrooms. Allow them to cook for about 3-4 minutes until tender. Then, pour in the light coconut milk and mix thoroughly.
Stir in the fresh lime juice and grated lime zest, then fold in the sliced scallions and chopped cilantro just before serving.
Ladle the soup into bowls and garnish with additional cilantro if desired. Pair it with a side of jasmine rice or enjoy it on its own.
