1. To make the roux,melt the butter and chocolate in a medium saucepan over medium heat. Once melted,add the remaining ingredients and cook for 2-3 minutes,stirring constantly,until a thick brown paste forms. Take off the heat and set aside.
2. Heat a splash of oil in a large saucepan over medium heat. Add the onion and garlic,and cook until softened and starting to caramelise,about 5 minutes.
3. Add the carrot and daikon,and cook for 5 minutes.
4. Add the potato and ginger,season and cook for 5 minutes.
5. Add the roux,stir to coat the vegetables,then add the stock and apple and bring to a simmer. Add the mirin and simmer gently for 20 minutes.
6. Add the okra and cook for 10 minutes until tender. Add the peas and simmer for a minute or so.
7. Check the seasoning,garnish with shallot and nori and serve with steamed rice.
Tip: For an optional garnish,rehydrate a handful of arame seaweed in water,dry well and shallow-fry until crisp,then sprinkle over the curry when serving.
Note:The origin of Japanese curry,or kare,can be traced back to the time of the British Raj. It's a long way from its source inspirations on the Indian subcontinent,but over time it has become incredibly popular – instant curry bases now line supermarket shelves in Japan.