Wash the asparagus and trim the tough ends of the stalks. In a large saucepan, bring 2 quarts of lightly salted water to a boil over high heat. Place the asparagus in the water and cook until just tender, 2-3 minutes.Drain asparagus. Add enough cold water to cover the asparagus. Let stand about 5 minutes, until the asparagus is cool.Drain again and pat the asparagus dry with paper towels. In a medium-size mixing bowl, whisk together the vinegar, oil, thyme, parsley, egg, onion, and capers, and salt and pepper to taste.Place the asparagus on a serving platter. Pour the vinaigrette evenly over the asparagus. Let the asparagus marinate in the dressing for a few minutes (optional). Garnish with additional chopped egg and parsley, if desired. Serve at room temperature.