Method: For the raita:Combine all the ingredients in a bowl. Whisk.Season well and set aside in the fridge for serving. For the lentil cakes:Rub sweet potatoes with olive oil and a pinchof salt. Make a few steam holes with a fork and roast them whole on a rack at180˚C until tender. Allow to cool and scoop out 2 cups of flesh. Cook lentils in 3 cups of boiling salted wateruntil very tender. Strain off all residual water and allow to cool. In a large frying pan heat a drizzle of oliveoil and fry the onion in the curry powder. Once tender add the garlic and cookuntil fragrant. Add the diced mushrooms and cook until they have released alltheir liquid and are beginning to brown. Remove from the heat. Place lentils, sweet potatoes, egg, corianderand chilli in the bowl of a food processor. Pulse until well combined. Add theflour and mix again. Finally add the cooked mushroom mixture and pulse to bringeverything together. For a healthier lentil cake:Preheat oven to 180˚C. Place them on a bakingtray lined with baking paper. Bake for 15 minutes, flip them over and bake foranother 15 minutes until golden brown. For a crispy lentil cake: Heat a few cms of neutral oil in a casserole.Dust lentil cakes in chickpea or wheat flour. Fry lentil cakes until golden brown and crispyall over. Drain on paper towel. Serve lentil cakes hot with raita, freshcoriander and lime wedges.