Pour the chicken bone broth into a pot and add the spice base. Bring to the boil.
Stir in the chicken, mushrooms, tomato, lemongrass, scallions and a tablespoon of fish sauce.
When the broth starts to boil, lower the heat, cover the pan and simmer for about 10 minutes.
Pour in the coconut cream.
Over medium heat and with the pot uncovered, continue cooking the soup over a gentle boil until the chicken and mushrooms are cooked through.
Taste the soup. Add more fish sauce if too bland.
Off the heat, stir in the lime juice.
Taste and adjust the amount of fish sauce and lime juice, if needed.