"Dirty leek !" or "Sâle poireau !" in French. It could be a way to make fun of your little brother but it's not ! If you're lucky, you're leeks grew in dirt and you'll need to wash them properly before cooking them.
But don't worry ! Julie from Burnt Carrots ("Les carottes sont cuites!") wrote a whole article on how to clean and prepare leeks ! It comes with great pictures so we asked her if we could use some for our course !
http://www.burntcarrots.com/recipes/how-to-clean-a-leek/
Visit the blog, it contains tons of recipes and more mouth watering pictures for vegetable lovers http://www.burntcarrots.com