Brazilian pork stew with corn dumplings

Name: Brazilian pork stew with corn dumplings
Prep time: 25 min
Cook time: 2 h 35 min
Total time: 3 h
Cuisine: Latin American
Ingredients: 900g pork shoulder cut into 4cm chunks; 2 tbsp sunflower oil; 2 onions finely chopped; 2 celery sticks, finely chopped; 3 bay leaves; 1 tbsp oregano leaves (or 2 tsp dried), plus extra, to serve; 1 tbsp ground cumin; 1 tbsp ground coriander; 1 tbsp allspice; 1 stock cube (beef, pork or chicken); 2 x 400g cans chopped tomatoes; 1 tbsp cocoa powder; 2 tbsp soft dark brown or muscovado sugar; 3 tbsp red wine vinegar; zest and juice 2 oranges; 2 red chillies halved lengthways - seeds in or out, depending on whether you like it spicy; bunch spring onions finely sliced; 400g sweet potatoes peeled and cut into 3-4cm/1.25in - 1.5in chunks; 2 red peppers deseeded and cut into chunks; 2 x 400g cans black beans drained and rinsed; 100g cold butter diced; 200g self-raising flour; 140g cornmeal or finely ground polenta, plus extra for dusting; ½ tsp bicarbonate of soda; 140g sweetcorn from a can, drained, or freshly cut from a cob (just boil for 3 mins first); 75ml buttermilk; 1 medium egg beaten