1. Cut the aubergines lengthways into 1cm-thick slices. Sprinkle with salt, layer in a colander and set aside to drain for 40 minutes.
2. Meanwhile, make the chermoula. Put the spices, harissa, lemon juice, herbs and 4 tablespoons of oil into a processor with a pinch of salt. Blend to a paste and stir in enough of the remaining oil to make a sauce.
3. Preheat the oven to 110°C/fan90°C/gas 1/4. Pat the aubergines dry with kitchen paper. In batches, brush with oil and barbecue over a medium heat for 5-6 minutes each side, until golden. Keep warm in the oven while you cook the remaining slices.
4. Place the aubergine slices on a serving dish, drizzle with the chermoula and sprinkle with the coriander leaves to garnish.
Preheat your barbecue in the usual way until it reaches the correct temperature. Cook turning once, bearing in mind you may have to adjust the cooking time slightly depending on how hot your barbecue is or how near the heat source the food is placed.