Heat the oil in a large saucepan. Add the onion and fry gently until soft but not coloured. Add the garlic, chilli powder, curry powder and turmeric to the pan and fry for 2 minutes until the spices become fragrant. Add the tomato purée, tomatoes and stock and bring to the boil, then reduce the heat and simmer for 10 minutes. If the stew becomes too dry, add a little more stock.
Stir in the monkfish and chickpeas and bring to the boil, then reduce the heat and simmer for 5 minutes, or until the monkfish is cooked. Finally, stir in the mango chutney and season to taste with a little salt and pepper. Serve in bowls, topped with a spoonful of yogurt and some coriander leaves.