Combine stock, galangal, lime leaves, and lemon grass in a large pot.

Bring to a boil and simmer for 10 minutes (or 20 if using regular stock).

Reduce heat to low and add lemon/lime juice, chilli paste, and fish sauce.

Simmer for a few minutes, stirring well to dissolve chilli paste.

Add mushrooms and chicken (or prawns).

Cook until the meat is fully cooked, being careful not to overcook shrimp.

Stir in coconut milk (shake the can well before opening).

Simmer on low heat for a few minutes, avoid boiling to prevent curdling.

Add fresh chillies (warn guests about the heat).

Garnish with coriander before serving.