Whisk sugar, egg yolks, cornstarch and salt in large bowl to blend. Gradually whisk in 3/4 cup half and half. Bring 1 1/4 cups half and half to simmer in heavy medium saucepan. Gradually whisk hot half and half into egg mixture; return mixture to saucepan. Whisk over medium-low heat until pudding thickens and comes to boil, about 5 minutes. Boil 1 minute longer, whisking constantly. Remove pudding from heat. Add chocolate, Frangelico and vanilla; whisk until chocolate melts and pudding is smooth. Divide among six 3/4-cup custard cups. Sprinkle hazelnuts over puddings. Refrigerate until cold, about 2 hours. (Can be made 1 day ahead. Cover; keep chilled.) Spoon whipped cream atop puddings, if desired. Serve with ladyfingers.