First, wash the leeks. Leeks are almost always sandy or muddy inside, so washing them thoroughly is a must. For this application, the easiest way is like so: Fill a sink with cool water. Meanwhile, cut away the upper, darkest-green part of the leek and discard. Next, remove the roots from the leek, but leave enough of the root end so that the layers of the leek are still attached together at the bottom. Split the leek in half lengthwise, leaving the bottom quarter-inch uncut so that the two halves are still attached. Place the leeks in the sink and swish them around vigorously. If necessary, pull the layers of leek apart at the top and use your fingers to dislodge any stubborn dirt clods. Let the leeks float for a minute to allow the dirt to settle to the bottom, then remove to a dry towel to drain.
Toss the leeks with the vegetable oil and season with salt and pepper. Place in a roasting pan and cook in a medium-hot wood oven, turning occasionally, until the leeks are soft and nicely caramelized. This will probably take somewhere between 20 minutes and half an hour, depending on the heat of your oven.
Meanwhile, make your vinaigrette. In a bowl, combine the shallot, honey, Dijon mustard and white wine vinegar. Season with salt and pepper and whisk to combine. Then, whisking constantly, slowly drizzle in the olive oil, tasting as you go. Use as much oil as it takes to get the vinaigrette to the level of sharpness you like, probably somewhere between 3/4 and 1 1/2 cups. Fold in the fresh chopped herbs.
When the leeks are done, remove from the oven and toss with the vinaigrette. Allow the leeks to marinate at least 10 minutes before serving – the longer the better. This is a dish that can be served room temperature, so make it as far in advance as you’d like and let the flavors marry. Makes a great accompaniment to anything rich you’ve roasted in your oven, from pork chops to sausages, or even a meaty, flavorful fish such as cobia or sturgeon.