Preheat the oven to 180°C (360F) and line a large baking sheet with parchment paper. Slice the aubergine length-ways in 2cm thick slices. If using small aubergines, slice them in half.
Use a knife to score the aubergine (flesh-side up) in a diagonal fashion, to form a "diamond" shape. Be careful not to cut through the aubergine or its skin. Place the sliced and scored aubergines on a plate and using a paper towel, pat them dry.
Place the miso paste, sake, mirin, rice syrup, and sesame oil in a small saucepan on medium-low heat (do not use high heat). Stir continuously until the mixture is incorporated and a shiny glaze is formed, around 2-3 minutes. Remove from heat.
Place the dried and scored aubergines on the baking sheet with parchment paper, flesh side up. Using a pastry brush, glaze the surface of the aubergines with a thick layer of the miso mixture. If there is leftover mixture, you can use this to re-glaze the aubergines after baking.
Bake in a pre-heated oven for 5 minutes at 180°C. Then, increase the oven temperature to 200°C (400F) and bake for a further 20-25 minutes. The total cooking time highly depends on the thickness of your aubergine. Thicker slices may require longer baking time.Miso glazed aubergines should be juicy but firm, and slightly charred. The miso glaze should be bubbly and slightly caramelized.
Remove from oven, allow to cool slightly and sprinkle with parsley, green onions, chives, or sesame seeds and enjoy warm!