Put the oil in a pan on the biggest burner and on the highest heat. When it’s very hot, add the curry leaves, cumin and mustard seeds, stir, then follow swiftly with the onion, garlic, chillies and courgettes. Leave to cook for two minutes, to get some char on the courgettes, stir again, then leave to cook for another two minutes. Add the turmeric, salt and pepper, and leave to cook and catch for a further four minutes.