To make a delicious sweet potato soup, toss a diced onion and 2 tbsp of olive oil in a large pot and cook until tender. Add a dash of curry powder, the flesh of 3 precooked sweet potatoes, and 5 cups of vegetable stock, then bring the mixture to a boil. Let cool, then pour into a blender. Process until smooth. Return to pot. Stir in a cup of coconut milk and 1/2 cup of water. Heat until warm.