Heat most of the oil in a deep-sided frying pan or shallow flameproof casserole dish over a medium-high heat and, once hot, cook the aubergines for 8-9 mins until well coloured. Reduce the heat to medium, add the remaining oil, add the onion and cook for 6-8 mins until soft. Add the garlic, ginger, curry powder and turmeric. Cook for a minute more, then add the tomatoes, soy sauce, honey or agave, the coconut milk and peanut butter. Cook for 15-20 mins until thickened and reduced. Once cool, will keep frozen for up to three months. Tip into freezerproof food bags and freeze flat. Defrost in the fridge overnight and reheat until piping hot.