Traditionally the leeks were cooked in a big pot of boiling water. However, it’s better to steam them, which prevents them from getting waterlogged. Smaller leeks, which appear in the springtime in Paris markets, are preferable for this dish because they’re quite tender, although larger leeks are just fine, too. Just make sure that you clean the leeks very well, and cook them until they’re completely soft all the way through.
When Romain and I made this together and we plated up the leeks, I got an unexpected lesson in the art of arranging the poireaux: I learned that it’s imperative you lay them with the queue (tail) alternating with the tête (head). So I recommend you follow those instructions, if you want don’t want to raise any Parisian eyebrows. —David Lebovitz
4 to 6
(200 g) thick-cut smoked bacon cut into lardons
To make the vinaigrette, cook the bacon over medium heat in a skillet until nearly crisp. Transfer the bacon to a paper towel to drain. When cool, chop the bacon into pieces about the size of tiny peas.
Whisk together the vinegar, mustard, and salt. Whisk in the oils, 1 tablespoon at a time (the sauce may emulsify, which is fine), then stir in 1 tablespoon of the parsley and two-thirds of the bacon. Set aside.
To prepare the leeks, fill a large pot fitted with a steamer with a couple of inches of water. Bring it to a boil over high heat and add the leeks. Cook the leeks until tender; when you poke them with a sharp paring knife, it should meet no resistance at the root ends. (Smaller leeks will take about 15 minutes, and larger ones will take about 30 minutes.)
Remove the leeks and let drain and cool on a plate lined with paper towels. Cut the leeks in half crosswise, and arrange on a serving platter, alternating them head to tail.
Peel and dice the hard-cooked eggs and scatter them over the leeks. Pour the vinaigrette over the leeks and toss them and the pieces of egg in the dressing so they’re thoroughly coated, then scatter over the remaining bacon pieces and parsley.