Dice approx. 100 g of the mango, cover and set aside. Cut the rest of the mango into pieces. Melt the butter. Sauté the onion. Add the pieces of mango and sweet potato, continue to cook. Add the lemon grass and cook briefly. Pour in the water, bring to the boil, season. Reduce the heat, cover and simmer for approx. 20 mins. over a medium heat until soft. Puree the soup, strain if necessary. Add the reserved diced mango, simmer for a further 5 mins.
Mix the coriander with all the other ingredients up to and including the pepper. Gradually stir in the oil. Place the baguette slices on a baking tray lined with baking paper.
Toast for approx. 5 mins. in the centre of an oven preheated to 220°C.