To make the curried roux, melt the butter in a pot over medium heat, add in the flour and stir to combine. Keep stirring until the mixture turns slightly golden, about 1-2 minutes. Mix in the Japanese Curry Blend and Garam Masala and cook for a further 30 seconds. The roux should be crumbly. Transfer to a bowl and set aside.
To make the curry sauce, into the same pot, add the butter, followed by the onion, garlic and mushrooms, and sauté for a few minutes. Then add the tomato paste and stir through for 30 seconds. Next, mix in the roux and the vegetable stock, stirring continuously and slowly as you pour to break up any clumps. Add the grated apple and remaining vegetables and bring to a simmer.
Cook gently for 5 minutes, making sure to remove any impurities that may rise to the top, then mix in the Worcestershire sauce, kecap manis and dark soy sauce. Continue to simmer on low heat until the vegetables are soft, about 15 minutes, stirring often to ensure it doesn’t stick. Adjust the seasoning to your liking by adding some extra soy sauce. Serve with steamed rice, pickled vegetables or ginger and sprinkle with black sesame seeds.
Worcestershire sauce is traditionally not vegetarian, however, there are various brands available on the market that do not contain anchovy. Use one of these to make this recipe vegetarian.