Sweet potato burgers

oil spray
1 oinon chopped
1 red capsicum, chopped
1 stick celery, chopped
1/2 bunch kale, stems and stalks removed, coarsely chopped (about 5 cups)
3 cloves garlic, crushed
1.5 tsp salt-free Cajum seasoning blend
1/4 tsp salt
2 medium sweet potatoes (about 460g) peeled grated
130g dried black beans, soaked overnight and boiled for about 45 mins, or until tender, drained
115g firm tofu, patted dry
2 tbsp polenta
3 tsp olive oil

1. Spray a large non stick frypan with cooking oil spray and heat over a medium heat. Add oinon, capsicum and clerey and cook for 8 mins, stirring, or until softened. Stir in kale, garlic, cajun seasoning and salt. Cook for 4 minutes, stirring or until kale wilts. Add sweet potato and cook for 10 mins, stirring or until softened. Set aside.
2. Combine black beans and tofu in a large bowl. Mash with a potato masher until smooth. Add potato mix and stir until well combined. Refrigerate for 30 mins to set.
3. Sprinkle 1 tbsp of polenta on a plate. Pack burger mix ina 1/2 cup measure and turn onto the plate. Press to form an 8cm thick patty. Set aside. Repeat to make 8 patties. Sprinkle with remaining polenta.
4. Cook in frying pan 4 at a time for 10 mins turning once or until hot and browned.