Fire up the barbecue. While the coals are still very hot, cook the aubergines whole until the skin is blackened and the flesh soft, then leave to cool in a bowl. (Alternatively cook the aubergines in a very hot oven for 20 mins or char on a hot griddle pan). Peel off the charred skin and chop the flesh. Tip into a food processor with the yogurt, lemon juice, garlic, chilli, coriander and olive oil and season with salt and pepper. Blend until smooth tip into a bowl, and drizzle with more olive oil. For a chunkier dip, the aubergine, garlic and chilli can be chopped by hand and mixed with the other ingredients.