Preheat oven to 400°.
Cut a piece of foil long enough to fit around a 1 1/2-quart soufflé dish, allowing a 1-inch overlap; fold foil lengthwise into thirds. Lightly coat one side of foil and bottom of dish with cooking spray. Wrap foil around outside of dish, coated side against dish, allowing it to extend 4 inches above rim to form a collar; secure with string or masking tape.
Snap off tough ends of asparagus; remove scales with a knife or vegetable peeler, if desired. Steam asparagus, covered, 3 minutes or until crisp-tender; drain. Thinly slice asparagus spears to equal 1/2 cup; set aside. Cut remaining asparagus spears in half; set aside.
Place flour in a medium saucepan. Gradually add milk, stirring with a wire whisk until well-blended. Bring to a boil over medium heat, and cook 3 minutes or until thickened, stirring constantly.
Place egg substitute in a large bowl. Gradually add hot milk mixture to egg substitute, stirring constantly with a wire whisk. Remove from heat; add cheese, stirring until cheese melts.
Place milk mixture, halved asparagus spears, mashed potatoes, dill, salt, and red pepper in a blender; process until smooth. Pour mixture into a large bowl; stir in sliced asparagus.
Beat egg whites and cream of tartar at high speed of a mixer until stiff peaks form. Gently stir one-fourth of egg white mixture into milk mixture. Gently fold in remaining egg white mixture.
Pour mixture into prepared soufflé dish. Bake at 400° for 10 minutes. Reduce oven temperature to 350°, and bake an additional 45 minutes or until puffed and golden. Remove foil collar, and serve immediately.