Make the curry
Melt half of the butter in a saucepan over medium-low heat.
Add the diced onion and a pinch of salt. Cook for 8–10 minutes, stirring occasionally, until the onions have softened and started to lightly caramelise.
Add the grated apple, carrot, potato and minced garlic. Stir well to coat everything in the buttery onions and cook for another 2–3 minutes.
Simmer
Pour in the chicken stock and bring to a boil.
Reduce the heat to a gentle simmer and cook for around 15 minutes, or until the grated vegetables have softened completely.
Add the curry
Add the Golden Curry cubes and stir until completely dissolved.
Add the light soy sauce, mirin, sugar or honey and Worcestershire sauce.
Stir well and simmer for another 5 minutes.
Blend the curry
Remove from the heat and allow the curry to cool slightly.
Carefully transfer to a blender and blend until completely smooth and glossy.
Return the curry to the saucepan and warm through over a low heat.
Turn off the heat and stir in a knob of cold butter until melted and glossy.
Taste and adjust the seasoning if needed.
Make the chicken katsu
Set up three bowls or trays: one with seasoned flour, one with beaten egg and one with panko breadcrumbs.
Coat each chicken thigh in the seasoned flour, shaking off any excess.
Dip into the beaten egg, then press firmly into the panko breadcrumbs until completely coated.
Heat around 1–2cm of neutral oil in a frying pan over medium heat.
Carefully add the chicken and fry for around 4–5 minutes per side, or until golden brown and cooked through.
Transfer to a wire rack and season with a little salt while hot.
Allow the chicken to rest for a few minutes before slicing into strips.
Make the sesame cabbage slaw
Add the toasted sesame seeds to a bowl and crush them using a pestle and mortar.
Add the Kewpie mayo, garlic, soy sauce, rice vinegar, sugar and sesame oil. Mix until smooth.
Add the finely sliced cabbage and toss until evenly coated.
Taste and adjust to your liking.
Serve
Spoon a generous amount of the curry sauce into a bowl alongside some warm short-grain rice.
Top with sliced crispy chicken katsu and serve with a pile of the Japanese sesame cabbage slaw.
Finish with finely sliced spring onions and a sprinkle of sesame seeds or furikake.