Clean the leeks thoroughly but leave the root end intact. Cut away the root fibers, but don’t cut off the area where the leaves attach to the base of the stem. Trim away the tough, dark green tops. Split the leeks in half lengthwise. Check for any dirt that may be inside the leeks and rinse again if needed.
Place the leeks in a single layer in a casserole or baking dish. Drizzle with the olive oil and sprinkle with the salt, pepper, and chopped fresh parsley. Turn the leeks several times to coat all sides with the oil and seasonings.
Bake for 15-20 minutes, turning once, until the leeks begin to blacken.
Cleaning the Leeks:Leeks are notoriously dirty. They grow upward through the dirt capturing it in their leaves as they go. I always try to find the cleanest ones available in the grocery store, but you just can't see what's really in there until you get them home and cut them. If you see more dirt when you split the leeks, gently rinse them again under cold water being careful not to pull the leaves off.Storing Leftovers: Store any leftovers in a sealed container in your refrigerator for up to three days.To Make in Advance: You can roast the leeks up to two days in advance of serving. Store the cooked leeks in the refrigerator and reheat them either in the microwave or in the oven until warmed through.