Leeks are notoriously sandy! Here’s how to thoroughly clean them:
Cut off the green leaves of the leek where they start to ‘Y’ just on top of the white portion and save the green leaves for all stocks. Do not remove the root end. Split the leek in half, lengthwise. Hold under cool running water while using your fingers to separate the layers. Rinse until all sediment is removed. Let drain, slice off the root ends and cut as your recipe requires.