Choose leeks that are about an inch thick and have a long, white and pale green shaft.
- 6 long leeks (about 2 to 2 1/2 pounds total)
- 1/4 cup olive oil
- 1 tablespoon red wine vinegar
- 1 teaspoon Dijon mustard
- 1/4 teaspoon Kosher salt
- 1/4 teaspoon finely ground black pepper
1 Bring a large, wide (12 inches) pot, half-full of salted water (2 teaspoons of salt for 2 quarts of water) to a boil. While the water is heating, clean the leeks, keeping them whole.
To do this, first rinse off any visible dirt from the leeks. Then, use the tip of a sharp knife to pierce the leek just a little bit below the point where the leek's shaft opens up into separate leaves.
Cut the leek from this point all the way out to the tip of the green leaves, keeping the shaft whole. Open up the leaves, and place the leek under running water to clean out any dirt or sand that may be hiding between the leaves.
Cut off the dark green tops, leaving about an inch or two (or three if you like the more strongly flavored greens) on the shaft. Cut off the roots, cutting as close to the roots as possible, to help keep the leek together while it simmers in the next step. (For a visual step-by-step, see How to Clean Leeks.)
2 Once the water is boiling, carefully place the cleaned and prepped leeks into the water. Return to a simmer and lower the heat to maintain a simmer. Start a timer and cook for 8 to 10 minutes, or until the thickest part of the thickest leek can easily be penetrated with the tip of a sharp knife.
If your leeks are about an inch thick, they should just begin to be turning from bright green to olive-y green at the 8 minute mark. Thicker leeks you'll want to cook a little longer. Use tongs to gently remove the leeks from the pot and place into an ice water bath to stop the cooking.
3 Remove the leeks from the ice water bath and let them drain. The best way to let them drain is to place them in a rimmed roasting pan and then propping up the pan at an angle so the water can run out of the leeks. Let them drain for 10 minutes or so while you make the vinaigrette.
4 Make the vinaigrette by placing the oil, vinegar, mustard, salt, and pepper, in a jar and whisking until well emulsified.
5 Place the leeks in a rimmed, long serving dish (a Pyrex casserole dish would work for this as well). Drizzle some vinaigrette over the leeks. Gently turn the leeks over and drizzle a bit more vinaigrette on the other side.
Cover with plastic wrap and let the leeks marinate in the vinaigrette for at least 2 hours, or up to 3 days. (Chill if marinating more than 2 hours. The longer they marinate, the tastier and more tender they become.) The leeks should be served at room temperature.
Alternative serving suggestion: cut the marinated leeks crosswise into 1-inch long segments and serve with strips of roasted red bell peppers that have been marinating in the same vinaigrette.