1tablespoon thai chili paste (optional, can also use Thai red curry paste)
3tablespoons lime juice
2tablespoons fish sauce
1tablespoon brown sugar
Direction
Bring coconut milk and broth to a boil, add thinly sliced galangal, minced ginger, and Thai chiles to soup - simmer for 10 minutes.
Add chicken slices and stir occasionally until chicken is tenderly cooked.
Add straw mushrooms and thinly sliced & deveined lime leaves.
(optional : cut a few cross-sections of the lemon grass and add to the soup)
(optional : cut tomatoes into largish cubes about 1/2" square, and add to soup).
(optional : if you are using fresh limes, zest the lime peel into the soup).
(optional : Add Thai chile paste or red curry paste).
Stir well and simmer for 5-10 more minutes.
Just before serving, turn off the heat, then add brown sugar, lime juice, fish sauce, and stir well.
Finisher's instructions: balance the flavors by adding more spicy (chile paste), sour (lime juice), or salty (fish sauce) until perfection is reached. Different brands may have different strength or acidity -- Be careful not to overdo any one dimension, and stir well inbetween
Top with cilantro, and serve hot by itself or pour over rice.
Leftovers are often even more flavorful the next day or two.