Choose leeks that are about an inch thick, and have a long white to pale green shaft. The pale parts are the most useable.
- Fresh leeks
Before getting started with either method, rinse the leeks under water to remove visible dirt or sand.
Preparing leeks for soup
1 Cut off the roots of the leeks. Slice the leeks lengthwise.
Decide how much of the leek greens you want to use. They are tougher and can be stronger tasting, but soften with long cooking. The last couple of inches of the dark green ends should probably be discarded or saved for making stock. (I put mine in a plastic bag and drop it in the freezer.)
Make crosswise cuts along the parts of the leek that you intend to use.
2 Place the chopped leeks into a bowl and fill with cold water. (If the leeks are especially dirty, rinse them first in a colander, before covering with water.) Use your hands to agitate the leeks and dislodge any dirt or sand that may be clinging to them.
Scoop the leeks out of the water with a sieve or slotted spoon and place in a new bowl.
Cleaning and Prepping Whole Leeks
1 Place leek on a cutting board. Insert the tip of a sharp knife about a 1/4-inch below the lowest opening in the leek. Cut straight through, up to and through the green ends of the leek, leaving the pale part of the leek whole.
2 Fan open the leek and place under cold running water. Rinse out any dirt or sand. If the leek is especially dirty, you may want to make another similar cut through the leek to further be able to fan the leek open.
3 Cut off the dark green tops of the leek, reserving on the body of the leek as much of the dark green as you want. We like the taste (it's basically just a big onion green), so we typically keep about 2 to 3 inches or so of the dark green part with the body of the leeks. Discard the dark greens or save them to flavor soups or stews, or use for making stock.
4 Cut of the root end of the leeks, staying as close to the roots as possible. Cutting close to the roots will hold the leeks together when cooking them whole.