Place egg in a bowl, and set aside. Combine sugar and cornstarch in a saucepan; stir well. Gradually add milk and maple syrup; stir with a wire whisk until blended. Bring to a boil over medium heat, and cook 1 minute, stirring constantly. Remove from heat.
Gradually stir one-fourth of hot milk mixture into egg; add to remaining milk mixture, stirring constantly. Cook over medium heat 1 minute or until thickened, stirring constantly. Remove from heat; stir in margarine and vanilla. Pour mixture into a bowl; place plastic wrap on surface and chill.
Per serving: 863 Calories; 14g Fat (15% calories from fat); 16g Protein; 171g Carbohydrate; 204mg Cholesterol; 262mg Sodium