Leeks are part of the allium family along with scallions, onions, shallots, chives and garlic.  Leeks have a more delicate onion flavor, sweet and mellow.  
Nutritionally speaking, leeks contain magnesium, vitamins A, C and K, folate and many others.  Rich in antioxidants and sulfur compounds, leeks protect the body against many diseases, reduce inflammation and helps with heart health, brain function and blood sugar.
Lots of benefits from the unassuming leek.
Storing Leeks before prepping:
Wrap the leek in plastic wrap or cut the leek and store in a plastic ziptop bag.  Use within a week.
How to clean leeks:
Soil is mounded around the growing leeks.  As the plant pushes through the soil, it is trapped between the many layers.  There will always be some dirt.  
One of the easiest ways to clean leeks is first to rinse any visible outside dirt off.  Trim and discard the root end.  Trim the tougher dark green tops off.  If you are a soup maker, stash those tops in your stock bag for a later date.  So much flavor in them!  The white and light green portions are the most tender.
Slice the leek lengthwise, right down the middle.  Flip each half, cut side down and cut the leek into thin slices.  Fill a large bowl with cold water, put the cut leeks in and swish the pieces around, separating with them with your fingers.  Any dirt should fall to the bottom of the bowl.  Using a slotted spoon or your fingers, remove the cut leeks and let drain on a paper towel or run the pieces through the salad spinner.
Leeks are perfect for quiche.
Pie crust – make it, buy it or go crustless.
Potato Leek Soup
Sauteed Leeks and Carrots
This is also delicious with a little bacon or pancetta and a side of rice or quinoa.