Thickly slice the aubergines and arrange over a grill rack. Brush lightly with oil, sprinkle with salt and pepper, then grill until browned. Turn them over, brush and season again then cook until tender, about 8-10 mins in total. Remove from the grill and cut each slice into quarters.
Drain and rinse the chickpeas, then tip into a bowl with the aubergine, coriander and red onion. Mix the dressing ingredients in a screw-top jar, shake well, then use to dress the salad.