Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper for easy cleanup.
Cut the aubergines in half lengthwise, then score the flesh in a diamond pattern, being careful not to cut through the skin. This allows the glaze to penetrate deeply.
Whisk together the peanut butter, miso paste, soy sauce, rice vinegar, honey, garlic, ginger, and oil in a bowl until smooth and well combined. If the mixture is too thick, add a tablespoon of warm water to loosen it.
Place the scored aubergines cut-side up on the prepared baking sheet and generously brush about two-thirds of the peanut butter-miso mixture over the cut surfaces, ensuring it gets into the scored cuts.
Roast for 20 minutes, then remove from the oven and brush with the remaining glaze. The aubergines should be starting to soften and caramelize.
Return to the oven for another 10-15 minutes until the aubergines are completely tender and the glaze is caramelized and bubbling. You should be able to easily pierce the flesh with a fork.
Transfer the roasted aubergines to a serving plate and garnish with sliced green onions, toasted sesame seeds, and cilantro if using.
Serve immediately while hot, either as a main dish with rice or as a flavorful side.