Blend sugar, corn starch and salt in a large microwave-safe bowl.  Whisk in milk and egg yolks until well blended.  Microwave on HIGH power for about 5 to 7 minutes, stirring every 1 to 2 minutes, cooking until pudding is thick and has boiled at least a minute.

Remove from microwave and stir in butter and vanilla. Pour pudding into a bowl to cool.  Cover surface with plastic wrap.

To assemble parfaits, place 2 tablespoons of graham cracker crumbs in each parfait glass.  Layer pudding and blueberries.  Garnish with whipped topping, if desired.

Gluten Free Modification:  Make sure to use gluten free graham crackers.