In a large saucepan saute leeks and carrots in olive oil until leeks are tender. Add potato and curry powder; cook and stir for 2 minutes.
Pour in stock, salt and pepper then bring to the boil. Reduce heat, cover and simmer for 15 to 20 minutes or until the vegetables are very tender.
Using a hand-held immersion blender, blend the soup in the saucepan until smooth. Alternatively, blend only part way so that some vegetable pieces remain. Alternatively, blend in batches using a blender.