Combine remaining 1 1/2 cups sugar and cornstarch in a large saucepan over medium heat. Gradually whisk in egg yolks and milk; cook milk mixture, whisking often, 12 minutes or until thickened. Bring milk mixture to a boil, and cook, stirring constantly, 1 minute. Remove mixture from heat; stir in butter and vanilla extract. Cover and chill 6 hours.
Spoon half of custard into 6 parfait glasses; top with half of sliced strawberries and 3 Meringues. Repeat layers, ending with 1 Meringue on top of each serving.