Mix sugar, cornstarch and salt in 2-quart saucepan. Gradually stir in milk. Cool over medium heat, stirring constantly, until mixture thickens and boils. Boil and stir 1 minute. Gradually stir at least half of the hot mixture into egg yolks. Stir into hot mixture in saucepan. Boil and stir 1 minute; remove from heat. Stir in margarine and vanilla. Pour into dessert dishes. Cover and refrigerate about 2 hours or until chilled. 4 Servings (About 1/2 Cup Each); 225 Calories Per Serving.To Microwave: Decrease milk to 1-3/4 cups. Mix sugar, cornstarch and salt in 8 cup microwavable measure or 2-quart microwavable casserole. Gradually stir in milk. Microwave uncovered on high 4 to 6 minutes, stirring every 2 minutes, until thickened and boiling. Stir at least half of the hot mixture gradually into egg yolks. Stir into hot mixture in measure. Microwave on medium (50%) 1 to 3 minutes, until thickened. Continue as directed.