4 medium sweet potatoes (About 1.5 kg)
2 tablespoons extra virgin olive oil
Sea salt flakes
400 ml can coconut milk, plus extra to serve
3½ cups (875 ml) chicken stock
1 stalk lemongrass, halved and bruised
5 cm piece ginger, halved
3 kaffir lime leaves
Dried chilli flakes, to serve
1) Preheat oven to 220°C (425°F). Place the sweet potato, cut-side up, on a large oven tray lined with non-stick baking paper. Drizzle with the oil and sprinkle with salt. Cover with aluminium foil and cook for 1 hour or until tender. Set aside until cool enough to handle.
2) While the sweet potato is cooking, place the coconut milk, stock, lemongrass, ginger and lime leaves in a large saucepan over high heat and bring to the boil. Remove from the heat. Remove and discard the lemongrass, ginger and lime leaves.
3) Using a spoon, scoop out the flesh of each sweet potato, discarding the skins, and place in a blender. Add half the coconut mixture and blend until smooth. Return to the saucepan with the remaining coconut mixture and cook over low heat, stirring constantly, until smooth and hot.
4) Divide the soup between bowls. Top with the extra coconut milk and sprinkle with chilli flakes to serve.