Snap tough ends off asparagus. Steam asparagus, covered, 2 minutes or until crisp-tender. Sprinkle with pepper. Toss with 2 tablespoons Preserved Lemon Vinaigrette; chill until ready to serve.
Combine crawfish, mâche, parsley, and remaining 2 tablespoons Preserved Lemon Vinaigrette, tossing to coat. Arrange 3 green and 3 white asparagus spears on each of 4 plates; top with about 1/2 cup salad mixture. Serve immediately.