Slice the aubergines, sprinkle with salt, and keep aside. In a mortar, pound together the red chillis, curmmin and mustard seeds. Mix with a little vinegar to make a smooth paste. Peel and halve garlic cloves, slit green chillis lengthwise and slice ginger finely. Heat a little of the oil in a pan and fry garlic, chillis and ginger for three minutes. Remove from oil and keep aside. Drain liquid from the aubergines and fry until brown and dry. Drain and remove from the pain. in the clean Saucepan fry the curry leaves and spice paste in remaining oil, for three minutes. Add vinegar and when nearly boiling add aubergines, garlic, chillies, ginger & tumeric powder. cook for two minutes add the sugar and salt to taste and cook for 10 minutes. cool and preserve in air tight bottles.