Whisk 1/2 cup sugar, cocoa and cornstarch in heavy large saucepan. Gradually whisk in milk. Whisk over medium heat until mixture boils and thickens slightly, about 4 minutes. Remove from heat.
Whisk yolks and eggs in large bowl. Gradually whisk in hot milk mixture. Return mixture to saucepan. Whisk over medium heat until mixture thickens, about 5 minutes (do not boil). Remove from heat. Add chocolate, butter and vanilla; whisk until mixture is smooth. Cool 10 minutes, whisking occasionally.
Spoon 1/4 cup pudding into each of 6 Champagne glasses. Top each with 4 raspberries. Repeat layering 1/4 cup pudding and 4 raspberries in each glass. Divide remaining pudding among glasses. Cool completely. Beat cream and 2 tablespoons sugar in large bowl to stiff peaks. Top parfaits with cream. Chill at least 2 hours and up to 8 hours. Top with remaining berries.
