Chana masala with pomegranate raita

Name: Chana masala with pomegranate raita
Ingredients: 1 tbsp rapeseed oil; 2 onions, halved and thinly sliced; 1 tbsp chopped ginger; 2 large garlic cloves, finely grated or crushed; 1 green chilli, halved, deseeded and thinly sliced; ½ tsp cumin seeds; ½ tsp mustard seeds; ½ tsp garam masala; ½ tsp turmeric; 1 tsp ground coriander; 400g can chickpeas, undrained; 4 small tomatoes (about 160g), cut into wedges; 2 tsp vegetable bouillon powder; cooked wholegrain rice, to serve (optional); 150ml plain bio yogurt; 25g pomegranate seeds; 2 tbsp finely chopped coriander, plus extra leaves to serve