Roasted aubergine & tomato curry

Name: Roasted aubergine & tomato curry
Prep time: 15 min
Cook time: 45 min
Total time: 1 h
Cuisine: Asian, Indian
Ingredients: 600g baby aubergines, sliced into rounds; 3 tbsp olive oil; 2 onions, finely sliced; 2 garlic cloves, crushed; 1 tsp garam masala; 1 tsp turmeric; 1 tsp ground coriander; 400ml can chopped tomatoes; 400ml can coconut milk; pinch of sugar (optional); ½ small pack coriander, roughly chopped; rice or chapatis, to serve