Prepare the fish by coating the pieces with flour and seasoning them with a suitable amount of salt and pepper. In a spacious frying pan, heat the oil and proceed to shallow fry the fish for approximately 2 minutes on each side. Afterwards, set the fish aside on absorbent paper to drain.
In a large pot, heat a mixture of vinegar and water over medium heat. Introduce the onions, sugar, salt, spices, jam, and bay leaves to the pot, and cook the ingredients for a duration of 8-10 minutes.
Next, incorporate the corn flour mixture into the pot, ensuring thorough stirring. Continue to stir the mixture well.
Transfer the fish, along with the cooked onion and curry sauce, to a heatproof dish of substantial size, ensuring that the sauce fully covers the fish.
Allow the dish to cool before covering it and placing it in the refrigerator overnight or for several days.