Peel the ginger and grate finely. Finely dice the pineapple. Bring the balsamic vinegar to the boil, stir in the sugar, add the pineapple and ginger and simmer until the flesh crumbles slightly. Stir in the curry powder and ketchup. Let simmer for approx. 4-5 minutes. Fry the sausages in the grill pan. Serve with the curry sauce.