Preheat the oven to 200C. Roast the sweet potatoes whole until just cooked (about 45 minutes - 1 hour). Turn off the oven, leave the potatoes to cool, then peel.
Place the sweet potato flesh in a bowl with the kneading hook; gently add the cumin, garlic, ground and fresh coriander, lemon juice and flour. Season well. Leave the mixture in the fridge to firm up for an hour or so.
Using a couple of soupspoons dipped in cold water, make the mixture into small patties and put them on an oiled baking tray. Bake in the oven for approximately 8 minutes on each side golden-brown. Serve with tahini, salad leaves and pitta bread