Place beef on a plate, mix miso, oil and 1 tbsp mirin in a small bowl to a paste and spread all over beef.
Preheat a bbq or chargrill plate to medium heat, cook beef for 3 minutes per side for medium rare. Rest for 5-10 minutes before slicing across the grain.
Bring a medium saucepan of water to the boil, cook soba for 2 minutes, add gai laan stems and cook for 30 seconds then add gai laan leaves and cook another 30 seconds, drain and return to saucepan. Gently stir through sesame seeds, carrot, radish, tamari, maple syrup and 2 tbsp mirin.
Serve noodles with pickled ginger, edamame, nori strips and top with sliced beef. Sprinkle with extra sesame seeds if desired.