Wash and peel the sweet potato. Chop into large cubes and steam for 10 minutes until softened. Remove from the steamer and allow to cool for 3 minutes.
Drain and rinse the chickpeas. Pat the chickpeas dry using a kitchen towel. Lightly mash half the chickpeas, being careful to leave a few whole, then set to one side
Add 200g of the whole chickpeas and a quarter red onion to the food processor.
Drain and pat dry the roasted red pepper. Add to the food processor along with the minced garlic, spices, salt and pepper. Pulse for 20 seconds.
Pour the mixture out into a large bowl and stir in the remaining 200g of lightly mashed chickpeas, quarter red onion and instant oats. This will help to add some texture to the patties. Season with extra salt and pepper.
Heat the oil in large non stick frying pan over a moderate heat.
Shape the sweet potato mixture into 6 patties.
Cook for 5 minutes, flip over and cook for a further 5 minutes.
Serve in a toasted bun alongside vegan cheese, grilled tomatoes, red onion, sriracha and mayo.