In a small bowl, mix together the sauce ingredients. Heat a large frying pan and pour in 1 tbsp of the oil. Season the aubergine and brown on all sides until soft (you may need to add another 1 tbsp oil as they cook) – this will take about 15 mins. Set aside.
Pour the remaining oil into a wok. Add the onion and garlic, and stir-fry for 3-4 mins on a low heat until the onion is soft and the garlic golden. Add the aubergine and pour the sauce over. Stir together, turn the heat down to low and cover with a lid for 2 mins. Take the lid off and stir-fry again for 1 min more. Serve with chilli slices and coriander sprinkled over.