While part of the allium family and easily substituted for onions, with a richer less bitter profile, leeks are not like a bigger version of the scallion.

Leeks are grown in sand or loose dirt, and grow in layers, trapping sand/dirt in between all of those layers, which makes cleaning leeks a more intense process than simply rinsing the outside as you would a green onion.

I have found that easiest way to clean leeks, is after you after you prepared them. And the easiest way to prepare them, is to slice off the bottom, and then to slice the leeks from top to bottom in half. Then run your knife through the white and light green parts creating half moon slices (further dicing if you need a smaller cut).

Once your leeks are cut, place them in a colander and rinse under cold water, while running your fingers through them to get out all the sand/dirt.

Once rinsed dry and use.