Make the curry ketchup: Add ketchup, tomato paste, and water to a medium pot. Heat until hot.
Add all the remaining ingredients and cook over low heat for 5-10 minutes, until the sauce is thickened.
Meanwhile, heat frying oil in a large frying pan over high heat. When hot, add the sausages and cook on both sides until brown. Transfer to a plate and cut into slices.
When the sauce is thickened, taste it and season to your taste if necessary (the amount of sugar and vinegar may be different for you, if you have used other brand of ketchup), season to taste with salt and pepper.
Serve sausage slices with curry ketchup and sprinkle more curry powder on top.
Enjoy!