Process onion, garlic, ginger and chilli in a small food processor until finely chopped. Heat oil in a large saucepan over medium heat, then add onion paste and sauté until fragrant (4-5 minutes). Add spices and stir until fragrant (1 minute). Add fresh tomatoes and cook until starting to soften (2-3 minutes). Add chickpeas and crushed tomatoes, and simmer for flavours to develop (about 15 minutes). Season to taste, stir in yoghurt, drizzle with molasses, top with coriander and serve with flatbread and extra yoghurt.