Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper for easy cleanup.
Prepare the aubergines by cutting them in half lengthwise, then scoring the flesh in a diamond pattern about ½-inch deep, being careful not to cut through the skin.
Brush the cut surfaces with vegetable oil, making sure to get into the cuts to ensure even cooking and prevent dryness.
Place the aubergine halves cut-side down on the baking sheet and roast for 20 minutes, or until the flesh is soft and tender when pierced with a fork.
While the aubergines are roasting, make the miso glaze by combining miso paste, mirin, sake, honey, and sesame oil in a small bowl. Whisk until smooth and well combined.
Remove the aubergines from the oven and flip them over so the cut side is facing up. Gently press down on the flesh to slightly flatten and create more surface area for the glaze.
Generously brush the glaze over the cut surfaces of the aubergines, making sure to get the mixture into the scored cuts.
Switch your oven to broil (grill) setting and return the aubergines to the oven, placing them about 6 inches from the heat source.
Broil for 3-5 minutes until the glaze begins to bubble and caramelize, watching carefully to prevent burning.
Remove from the oven and garnish with toasted sesame seeds, sliced spring onions, and cilantro leaves if using.
Serve immediately while hot for the best flavor and texture experience.