In a blender blend together the jalapeno, the vinegar, the mustard, the sugar, the salt, and the hot sauce with the motor running add the oil in a stream, and blend the dressing until it is smooth. Transfer the dressing to a large shallow dish and stir in the caraway seeds and the zest.
In a kettle of salted boiling water simmer the leeks for 7 to 10 minutes, or until they are just tender, and with tongs transfer them to paper towels to drain. Brush the cut sides of the leeks lightly with some of the dressing and grill the leeks, cut sides down, on a rack set about 6 inches over glowing coals for 1 to 2 minutes, or until they are golden brown. Transfer the leeks to the dish of dressing, turning them to coat them well, and let them marinate, covered and chilled, overnight. Serve the leeks at room temperature.
Recipe courtesy of Gourmet Magazine