Slice off the top third of the garlic at an angle, place the bulb on a baking tray or in an oven-proof dish with the cut side facing up, drizzle with oil, season.
Bake for approx. 30 mins. in the centre of an oven preheated to 180°C.
Allow the garlic to cool a little. Remove the soft cloves with a knife, set aside.
Heat the oil in a wide-bottomed pan, sauté the leek for 2-3 mins., add the sweet potatoes, briefly cook, season. Add the stock and tomatoes, simmer on a low heat for approx. 30 mins. Add the roasted garlic 5 mins. before the cooking time is up. Blend the soup, serve in bowls or soup plates. Drizzle with coconut milk, garnish with chilli flakes and cress.