To make the sauce, heat the oil in a large pan and add the onion, carrot and apples. Cover and cook gently for 10 mins until softened, stirring a couple of times. Uncover the pan, turn up the heat, add the garlic and cook for 1 min.
Stir in the curry powder and ginger. Cook for 1 min more, then stir in the tomato purée, honey, soy and cornflour. Gradually stir in the stock and simmer for 5 mins until the vegetables are totally soft and the sauce has thickened. Blitz with a blender or in a liquidiser until smooth, then season to taste with the sesame oil, salt and pepper. The sauce can be made up to 3 days ahead.
While the sauce is cooking, put the pork between 2 sheets of cling film and bash with a rolling pin until the meat is about 1cm thick. In a shallow bowl, rub together the crumbs, turmeric and oil with some seasoning. Beat the egg white with a fork until a little frothy and have a non-stick baking tray ready.
Put the rice in a saucepan with 400ml cold water and a pinch of salt. Bring to the boil, cover, then simmer for 10 mins. Take off the heat and set aside until ready to serve the pork.
Heat oven to 220C/200C fan/gas 7. Dip each piece of pork into the egg, then the crumbs, pressing them onto the surface before transferring the meat to the tray. Bake the pork for 10-15 mins or until golden and crisp, turning once if needed. Serve with the rice and katsu sauce, garnished with coriander, if using, plus pickled ginger, if you like.