Leeks vinaigrette with hard-boiled egg

I've read other bloggers' glowing descriptions of leeks vinaigrette, but the dish never really appealed to me. Boiled leeks, really? How could that be good? So I never bothered to try it, until I saw the recipe in Around My French Table. It includes a grated hard-boiled egg - which resembles mimosa flowers, according to Dorie Greenspan - and this made the dish sound just interesting enough that I decided to finally try it...and it was delicious. I should have known better than to doubt a dish that is a French classic. It was nice to let the leeks be the main component of the dish, instead of chopping them up and using them as an aromatic like I usually do - this preparation really showed off their delicate flavor.

Leeks vinaigrette with hard-boiled egg
Adapted from Around My French Table
Serves 4

16 young leeks, as fresh and thin as possible
1/2 tsp Dijon mustard
1 tbs sherry vinegar
2 tbs walnut oil
1 tbs extra-virgin olive oil
Salt and freshly ground black pepper
1 hard-boiled egg, chilled or at room temperature*

Trim leeks so that only the white and palest green parts remain, and cut off the roots. Split the leeks down the center, stopping before you cut through the stem end, and rinse leeks thoroughly. Divide the leeks into two bunches and tie each bunch together with kitchen string. Bring a large pot of salted water to a boil and drop in the bunches of leeks. Lower the heat so that the bubbles are steady but gentle, and cook the leeks until tender, about 10-20 minutes (when done, you should be able to easily pierce the leeks with the tip of a sharp knife).

While leeks are cooking, whisk together the mustard, vinegar, and oils in a small bowl, and season with salt and pepper.

When leeks are tender, lift them out of the water and pat them dry with a dish towel or paper towels. Place leeks on a serving platter, pour on the vinaigrette, and let them cool for a few minutes. Grate the hard-boiled egg over the leeks and serve immediately.

* To make the perfect hard-boiled egg, put the egg in a large heavy pot and cover with 1 1/2 inches of cold tap water. Partially cover the pot and bring water to a rolling boil. Reduce heat to low, cover pot completely, and cook eggs for 30 seconds. Remove from the heat and let eggs stand in the hot water, still covered, for 15 minutes. Then run the eggs under cold water (or place in a bowl of ice water) for about 5 minutes to stop cooking and prevent yolk discoloration.