Finely chop the onion and garlic, sauté in the butter. Add the quince jelly, curry and thyme, briefly sauté.
Pour in the stock and cream, bring to the boil, reduce the heat, cover and simmer for approx. 15 mins. Remove the thyme. Puree the soup until smooth, season.
Cut the fish into strips approx. 2 cm wide, add to the soup and leave to infuse for approx. 8 mins. Plate up the soup and garnish with curry and thyme.