Pulse garlic clove in a food processor or blender 3 to 4 times or until chopped. Add egg yolks, lemon juice, salt, and pepper; process until smooth, stopping to scrape down sides. With processor running, gradually add truffle oil and olive oil in a slow, steady stream, processing until thickened.
Snap off tough ends of asparagus spears. Cook asparagus, covered, in boiling salted water to cover 2 minutes or until crisp-tender; drain. Plunge asparagus into ice water to stop the cooking process, and drain. Arrange asparagus on a serving platter. Garnish, if desired. Serve with aïoli.
*One-fourth cup egg substitute may be used in place of the egg yolks. Two tablespoons warm water may be added to thin aïoli.