Leeks Vinaigrette

Trim the root end and any tough dark-green tops from each leek. Split each lengthwise from the top to within 2 cm of the root end, leaving them attached at the base. Fan open and wash under cold running water to remove all grit between the layers. Bring a large pot of well-salted water to a boil. Tie the leeks loosely in pairs with kitchen twine to keep them together. Lower into the water. Cook at a gentle boil for 18 to 22 minutes until completely tender throughout.

Lay the cooked leeks on a folded kitchen towel or rack in a single layer. Remove the twine. Let them cool to room temperature — about 20 minutes. Do not refrigerate. Press them gently to extract some of the cooking water, but do not squeeze hard enough to damage the layers.

In a small bowl, combine the minced shallot, Dijon mustard, vinegar, salt, and pepper. Let stand for 5 minutes — the vinegar will soften the sharpness of the raw shallot. Then whisk constantly while drizzling in the olive oil in a thin, steady stream to form a stable emulsion. The vinaigrette should be thick and creamy, not broken or oily.

Arrange the cooled leeks cut-side up on a serving platter or individual plates. Spoon the vinaigrette generously over them, letting it pool in the cross-section rings. Scatter the chopped parsley over the top. If including the egg mimosa, press the hard-boiled egg through a sieve or crumble it finely by hand over the dressed leeks. Serve at room temperature.