This isn’t a lesson or anything, except for the obvious one: For the love of God wash your leeks. Split ’em first, because the mud gets down deep. I don’t know what kind of hipboots it takes to be a leek farmer, and I don’t want to know what farming techniques or growth patterns seal that mud so damn far down, but jeez oh pete, that shit is nasty. On the flipside, I’d be nervous if I got a leek that wasn’t muddy. I’d feel like it was grown in a lab, or made in Captain Picard’s replicator, or something.
One quick semi-related tip: Anyone making potato leek soup should do what Julia Child did, and run it through a food mill. I love stick blenders, but I’m never using them on potatoes or leeks again. Food mill doesn’t glue up the potatoes, and it doesn’t let the super stringy parts of the leek through. You get fluffy flavorful soup that you don’t have to futz with to get the right consistency. More on soups later. For now, just wash your damn leeks!
You Make It You Eat It 
I’ve noticed that too with the leeks I’ve used. I always open them up to wash (and gross if you don’t!).