Remove any skin from the fish fillets and then cut them into small pieces. Combine all the fish cake ingredients, except for the oil, in a food processor with 1 tsp of salt and 2 tbsp of water and blend the mixture until it’s a firm paste.
Form the paste into two cakes, about 1cm thick. Heat the oil in a wok or large frying pan and fry each cake for 3-4 minutes on each side until golden. Remove with a slotted spoon and leave to drain and cool on paper towels.
While the fish cakes are cooling, soak the mushrooms in warm water for about 20 minutes until soft. Rinse well in cold water, drain, and set aside. When the fish cakes are cool, slice them into finger thick bite-size pieces.
Tip the oil out of the wok, leaving about 11⁄2 tbsp. Reheat the wok over a medium heat, add the garlic, ginger and onion wedges and stir fry for 1 minute. Add the courgette, cucumber, squash (if using), mushrooms and chicken stock and stir fry for another 2 minutes. Mix the sauce ingredients together then pour into the stir fry and continue to cook for another 2 minutes or until the vegetables are cooked. Return the fish cake pieces to the pan and mix gently to heat through. Serve at once with boiled rice.