In a medium saucepan combine cornstarch and milk; add corn syrup and margarine or butter. Cook and stir over medium heat until thickened and bubbly. Cook and stir 2 minutes more. Remove from heat. Stir in brown sugar and vanilla. Cool slightly, about 5 to 10 minutes. Just before serving, stir in nuts.

Serve warm over ice cream.

Cool mixture and store in a covered container in the refrigerator up to 1 week. To serve sauce that has been chilled, reheat in a saucepan over low heat until warm. Or, microwave 1 cup of the mixture in a glass measure on 100 percent power (high) for 1 to 1-1/2 minutes or until warm, stirring once. Stir in nuts just before serving. Makes about 3-1/2 cups (twenty 1/4-cup servings).

To give this sauce as a gift, spoon it into decorative jars. Tie the nuts in plastic bags and attach them to the jars with a serving spoon or ice-cream scoop. Stick on a label with directions for storing and reheating the sauce. Decorate with fancy ribbon.