Peel and dice the sweet potatoes. Peel the onions, garlic, ginger and carrots. Wash and clean the fennel. Finely dice everything.
Heat the oil in a saucepan. Fry the onions, carrots and fennel lightly. Add the ginger and garlic and continue to fry while stirring. Add cumin, coriander, garam masala, turmeric and chilli and roast for about 1 minute. Then add the tomatoes and simmer for 10 minutes. Add the sweet potatoes and coconut milk and cook over a low heat for about 25 minutes until the sweet potatoes are cooked through.
For the raita, peel and grate the cucumber. Mix with yogurt, salt and cumin and serve with the curry - it will soften the spiciness.
If you take soy yogurt instead of normal yogurt, it is a delicious vegan dish.