Heat oven to 220 C / 425 F. Line a sheet pan 33 x 46 cm / 13 x 18 inch with foil.

Pierce the eggplants several times with a fork and set them on the pan. Roast for 45 to 50 minutes, turning once, until the skin is blistered and black and the eggplants have collapsed and feel very soft.

Let the eggplants cool for about 15 minutes, until easy to handle. Cut in half lengthwise and scoop the soft flesh into a colander, discarding the charred skins.

Let the flesh drain in the colander for 10 to 15 minutes, pressing gently with a spoon to squeeze out excess liquid. This step keeps the dip from turning watery.

Chop the drained eggplant flesh finely with a knife, or pulse it 3 to 4 times in a food processor. Don't over-process, or the dip turns gray and gummy.

Transfer the chopped eggplant to a mixing bowl. Add the minced garlic, lemon juice, olive oil, tahini if using, salt, and pepper.

Mix everything with a fork until combined but still a little chunky. Taste and add more salt or lemon juice if needed.

Fold in the red onion and half the parsley.

Spoon into a serving bowl, drizzle with more olive oil, and scatter the rest of the parsley on top. Serve at room temperature or chilled.