Peel the sweet potatoes and cut them into big cubes. Place them in the steamer and steam them for about 15 min (maximum) or until they are firm and soft (not runny).
Preheat the oven 200 C (fan).
Mash the potatoes with a fork until nearly smooth but still chuncky.
Add all the other ingredients to the potatoes (½ cup oat flour, tomato puree, garlic, spring onion, tahini, cumin, chili, paprika, salt & pepper). And mix them all together with a fork.
Make the patties using an ice cream scoop: scoop out balls of the mixture, and place them directly on a tray lined with baking paper. Sprinkle all of them with oat flour.
Then flatten the balls into patty shape using a spoon.
Reduce the oven temperature to 180 C (fan) and place the tray for about 35-40 min in the oven or until the patties start to turn golden and crispy. Check out regularly and flip patties carefully after 20 minutes of cooking time.
Meanwhile, you can prepare the vegetable ratatouille.