Preheat your oven to 190°C/375°F/gas mark 5.
Peal and chop the sweet potato into small cubes, drizzle with extra virgin olive oil and cook for 25-30 minutes in the oven, turning occasionally.
Meanwhile rinse and drain your beans and place in to a large mixing bowl. With a masher, mash until roughly half the mixture becomes a paste.
In a frying pan add the onions and cook until caramelised. Add these to the bean mix then add the spices and sweet corn.
Once the sweet potato is done, mash well before adding to mixing bowl. Mix well. Add the brown rice flour to bind and continue to stir.
Shape into 8 large patties and place in the fridge to cool.
To cook: in a frying pan, drizzle olive oil and fry the burgers for 3 minutes on each side. Place on a baking tray and cook at 190°C/375°F/gas mark 5 degrees for a further 10-15 minutes until crisp. Alternatively drizzle with olive oil and grill on a BBQ.