Bolivian Bean and Sweet Potato Bake

Ingredients
TOPPING
 * 3 	 tablespoons   olive oil
 * 1 	large onion, halved and chopped
 * 2 	red peppers, roughly chopped
 * 1 	stalk celery, chopped
 * 2 	teaspoons ground cumin
 * 2 	teaspoons ground cinnamon
 * 2 	garlic cloves, peeled and crushed
 * 1 	red chili, chopped (mild)
 * 3/4 	ounce dark chocolate
 * 2 	tablespoons tomato puree
 * 2 1/4 	cups vegetable stock
 * 1 (14 	ounce) can kidney beans, drained
 * 14 	ounces sweet potatoes, peeled and chopped
 * 1 (14 	ounce) can sweetcorn (in water)
 * 3 	tablespoons cornmeal (instant polenta)
 * 1 	large egg, beaten
 * 1/2 	teaspoon paprika
 * 1 	tablespoon sugar
 * 1 	pinch salt

Directions

 * 1) Heat the oil in a large saucepan and cook onion, peppers and celery for 8 minutes; stir in the next 9 ingredients (or in other words, everything except the topping ingredients) and simmer for 25 minutes; spoon the mixture into a large oven proof dish.
 * 2) Preheat the oven to 375 F / 190 C /gas mark 5.
 * 3) Drain off 4 tbsps water from the sweetcorn, then whizz the rest of the contents of the tin in a blender; place pureed sweetcorn in a saucepan, add polenta and stir and simmer to thicken.
 * 4) Allow to sweetcorn mix to cool then beat in the egg; spread the mix over the filling and sprinkle over with paprika, sugar and salt.
 * 5) Bake for 35 minutes.