Simple as they are to make, and hearty when they're made just right, sometimes, the flavor of your soup just falls a bit flat. If you just so happen to have this secret ingredient handy, no matter what it is that's cooking on the stove - be it a hearty minestrone or a chicken noodle soup - you can fix its flavor in a pinch. It's called kombu, and it's one heck of an umami powerhouse.