Whisk hot pepper paste, sake, soy, mirin, dried chilli, garlic, ginger, and sesame oil into a smooth paste.
Wrap lamb bones in foil to prevent burning.
Brush racks with half the marinade and refrigerate overnight.
Preheat the oven to 180°C.
Sear lamb in olive oil in an ovenproof pan until golden and brush with more marinade.
Roast for 10-12 minutes and rest for 5 minutes.
Whisk sesame seeds, paste, miso, ginger juice, dashi, vinegar, lemon juice, and oil for the dressing.
Wilt the spinach in a hot frying pan.
Mix wilted spinach with yama gobo and the sesame dressing.
Slice lamb into chops and serve over a pile of sesame spinach with remaining marinade.