Start by slicing the aubergine in half lengthways and carefully make shallow cuts in a criss-cross diamond pattern in the flesh of both halves. Brush the cut sides of the aubergine halves with a little oil.
Place a skillet or frying pan over a medium heat, add the aubergine halves cut-side down and cook for a few minutes until the cut sides start to brown, then turn them over and cook for a few more minutes skin-side down until completely soft. Liquid will start to come out of the aubergine into the pan – that’s a good sign.
Preheat the grill to medium.
Mix together the ingredients for the miso marinade in a bowl and taste it. It should have a delicious savoury flavour – add more miso, brown sugar, vinegar and/or sesame oil as you see fit. Remember, the aubergine is quite bland so you want the marinade to have a really punchy flavour.
Put the aubergine halves on a grill tray cut-side up. Brush half the marinade over each aubergine, on the cut side, and grill for a few minutes until the miso marinade sizzles and caramelises slightly. Remove from the grill and scatter sesame seeds on top. Eat while warm.