Cut off and discard the root end and most of the dark green tips of the leeks, keeping most of the light green part near the white.
Pull away and discard any old and discoloured leaves.
Cut the leeks in half lengthwise, leaving about 5 cm at the root end uncut.
Thoroughly wash the leeks under cold running water, fanning out the layers to remove any trapped dirt. Drain well.
Cut the leeks into 18 cm (7 inch) pieces. Tie each leek with twine, securing at both ends.
Place the prepared leek into a large pot, add the stock or water and bring to the boil. Put the lid on the pot, turn down the heat and simmer for 40 – 50 minutes.
Use tongs to remove the leeks from the stock, transfer to a wire rack placed on top of a tray and allow to drain and cool with the twine still in place.
Combine the dressing ingredients in a small bowl and mix well and put aside.
Arrange the cooled leeks on a serving platter, remove the twine then drizzle over some of the dressing. Garnish with a sprinkling of finely chopped red onion and chives then serve.