I recently watched the Jazzy Vegetarian show and saw her make 4-ingredient leek soup. I decided within a couple of days to make it myself. We liked it! It is a very light soup and has a good flavor. It also gave me a reason to use leeks, so that's a good thing.
You can find the link to the 4-ingredient leek soup here (4th recipe down the page). Below are pictures from my experience making it.