Slice the aubergines in half lengthways and spread out in a shallow dish.
Combine the miso, oil, mirin, honey, chilli flakes and ginger. Pour over the aubergines and lightly season, turning them to coat. Leave to marinate for 30 minutes.
Heat your griddle pan and add the aubergines, in batches if necessary. Cook for 3-4 minutes on each side until tender and caramelised, basting with the marinade still in the dish as you go along.
Arrange in a platter and scatter over the spring onions and sesame seeds to serve.