1. In a large saucepan, heat the olive oil over medium heat. Add the onions. Cook them, stirring frequently, for 5 minutes or until they soften. Add the curry and the ginger, and cook another 5 minutes, letting the onions brown along the edges.

2. Add the mango flesh to the cooked onions. Add the water and orange juice, and let the mixture simmer for 15 minutes.

3. Purée the mixture in a food processor or blender, in batches if necessary. Then pass the purée through a sieve into a bowl, pressing with a rubber spatula or spoon to extract all the liquid.

4. Stir in the yogurt, salt, pepper, and cilantro. Chill the soup for at least 1 hour, preferably 2.

5. To serve, fancifully squirt or lightly spoon hot sauce on top of each bowl of soup. Accompany each serving with a wedge of lime, and urge your friends to squeeze the lime into the soup.