Heat the grill to its highest setting. Cut the aubergines in half lengthways and grill them, skin side up, close to the heat source, until the skins have blackened and cracked, and the flesh inside is very soft.
Meanwhile, peel, quarter and thinly slice the onions. Cut open the chillies lengthways under running water, remove the seeds and stems and finely slice the flesh crossways. Halv