In a medium to large saucepan place the butter, oil, leeks and 1 tablespoon of water. Cover with the lid and cook for 5 minutes, giving a stir every now and then.

Add the remaining ingredients except for the cream, bring to the boil and then simmer for about 25 minutes or until all the vegetables are cooked.

Using a stick blender, blend the soup until you have a smooth texture. Check and adjust seasoning.

Add a dash of cream to the soup if you would like.

Serve with some lovely toasted bread.