Mocha Pastry Cream:
Combine water and sugar in small saucepan. Bring to boil over medium-high heat, stirring until sugar dissolves. Remove from heat. Mix in Cognac. Cool.
Make Mocha Pastry Cream
Combine milk and espresso powder in heavy medium saucepan. Scrape in seeds from vanilla bean; add bean. Bring to simmer. Remove from heat. Discard bean. Using an electric mixer, beat yolks and sugar in large bowl until very thick, about 3 minutes. Sift in cornstarch; beat to blend well. Gradually beat hot milk mixture into egg mixture. Return mixture to saucepan. Whisk over medium heat until mixture comes to boil, about 3 minutes. Remove from heat. Add chocolate. Whisk until chocolate melts and mixture is smooth. Transfer to medium bowl. Place the plastic wrap directly onto surface of pastry cream. Refrigerate until cold, about 3 hours. (Can be made 2 days ahead. Cover syrup and store at room temperature. Keep pastry cream refrigerated.)
Yield: 8 servings.