Trim off the root end and dark green tops if needed
Slice the leek lengthwise from top to bottom
Rinse the layers under cold running water
Fan the layers apart to remove trapped dirt
Soak the cut leeks in a bowl of cold water if very dirty
Swish them gently to loosen grit
Lift the leeks out of the water so dirt stays behind
Repeat with fresh water until no grit remains
Drain well before using