Start by preparing the aubergine, preheat your oven to 180°C, slice the aubergine into quarters lengthways and place in a bowl, pour over the coconut milk and leave aside to soak. Ensure that the slices are well coated in the coconut milk as this will help the crumb to stick.
Next to prepare the coating, sprinkle the breadcrumbs across a plate and then sprinkle over the ½ tsp salt and ½ tsp black pepper.
Drizzle 2tbsp of oil over the base of a baking tray and then one by one dip the soaked slices of aubergine in the crumb and coat all over and place on your oiled baking tray. Sprinkle over any of the excess crumbs. Do not discard the remaining coconut milk and retain it to add to the sauce. Place the tray of crumbed aubergine in your hot oven and leave to roast for 25 minutes.
As the aubergine is roasting, make the Katsu sauce. In a saucepan, heat 3 tbsp oil and add in the diced onion and salt. Fry for 10 minutes or until softened on medium heat. Reduce the flame to low heat and add in the garlic and ginger pastes and fry for 1 minute.
Add in the white pepper, chilli, coriander, cumin, turmeric and paprika, stir and fry with the onions for 2 minutes. Add in a splash of water if the pan is becoming too dry. Once the spices have fried out for 2 minutes, stir in the plain flour and mix it will the spiced onion base.
Next, bit by bit, pour the vegetable stock into the sauce base, whisk well to remove any lumps. Carry on doing this until you have poured in all the stock. Once all the stock has been whisked into the sauce, stir in the remaining coconut milk and simmer the sauce on low heat for 2-3 minutes.
By now, the aubergine should have had 25 minutes of roasting time, once the aubergine has softened and cooked through remove the tray from the oven and leave in a warm place whilst you finish the sauce.
Returning to the sauce, add in the palm sugar, soy sauce and sesame oil and allow to simmer on low heat for a further 2 minutes, the sauce should be of a thickened 'coating consistency'. Serve the aubergine with the katsu sauce drizzled over and garnish with the sliced spring onion and crushed chilli. The curry can be accompanied by rice and a Japanese salad.