Preheat oven to 200°slice the eggplants in half and diagonally score the flesh, brush the cut half with olive oil and sprinkle over a little salt and pepper. Lay cut side down on a greased baking tray and bake for 20 minutes.
While the eggplant bakes, combine the miso, mirin, sake and sugar in a small saucepan and heat over medium stirring constantly until thoroughly mixed. Set aside.
Remove eggplant from the oven, flip and brush the cut side with the glaze then return to the oven and bake a further 10 minutes. Remove from the oven, brush over another layer of glaze and bake for a further 10 minutes.
Remove from the oven, brush over a final layer of glaze and allow to cool slightly before serving.