For the lamb, place the hot pepper paste, sake, soy, mirin, dried chilli, garlic, ginger and toasted sesame oil into a bowl and whisk together to form a smooth paste.
Wrap the lamb bones in small pieces of tin foil and pinch tight to prevent them burning.
Lightly brush the lamb racks with half of the hot pepper marinade (reserving the rest for later) and place the lamb onto a tray. Transfer to the fridge to marinate overnight, preferably for 24 hours. Allow to return to room temperature before cooking.
Preheat the oven to 180C/365F/Gas 4.
Heat a large ovenproof frying pan until hot and add the olive oil and marinated lamb. Cook on each side until golden-brown all over, then brush all over with some more of the marinade (reserve a little marinade for serving).
Transfer to the oven and cook for 10-12 minutes, or until cooked to your liking. Remove from the oven and leave to rest in a warm place for five minutes.
For the sesame spinach, place the sesame seeds, sesame paste, sweet white miso, ginger juice, dashi stock, rice vinegar, lemon juice and sesame oil into a bowl and whisk together to combine.
Heat a frying pan until hot, then add the spinach and cook until just wilted.
Add the yama gobo and the sesame dressing mixture and mix to combine.
To serve, spoon the sesame spinach into the centre of each plate in a neat pile. Slice the lamb rack into chops and place four onto each plate, arranged over the spinach. Add a little of the remaining marinade to each plate and serve.