How to Make It
Fill a large bowl with ice water. In a large saucepan of salted boiling water, blanch the leeks until tender, about 12 minutes for the baby leeks and 25 minutes for the medium leeks. Drain, then transfer to the ice bath to cool, 5 to 10 minutes. Drain well. Cut the baby leeks crosswise into 3-inch pieces and halve the medium leeks lengthwise; drain well on paper towels.
Meanwhile, preheat the oven to 400°. Spread the hazelnuts in a pie plate and toast for 5 minutes, until golden. Let cool, then coarsely chop.
In a medium bowl, combine the vinegar, shallots, lime juice and honey. Slowly whisk in both oils. Season the vinaigrette with salt and pepper.
Arrange the leeks on plates and season with salt and pepper. Drizzle with three-quarters of the vinaigrette and sprinkle the hazelnuts and parsley on top. Serve with the remaining vinaigrette.