Bring coconut milk, laksa paste, tomato purée and chilli jam slowly to the boil, uncovered, in a saucepan. Reduce heat and simmer for 5 minutes, or until oil rises to surface.
Add stock and return to the boil, uncovered. Reduce heat and simmer gently for 10 minutes. Season with lime juice and fish sauce. Taste and, if necessary, adjust seasoning.