Peel onions and ginger. Dice both finely. Put sugar and onions in a pot and caramelise while stirring occasionally. Add ginger, vinegar, 1/2 tsp salt, 1 tsp curry and tomatoes. Let simmer for 25-30 minutes at low heat while stirring occasionally.
In the meantime, cut the sausages several times. Heat oil in a pan. Fry the sausages for 8-10 minutes while turning. Season chutney with salt, pepper and sugar. Cut the mango off the stone.
Peel and dice the flesh. Wash parsley, shake dry, pluck off leaves and chop finely, except for a few for garnishing. Stir into the sauce with the mango.
Arrange sausages with the chutney on plates. Sprinkle with remaining curry. Garnish with parsley leaves. Ciabatta tastes good with it.