Heat the oven to 375 degrees F. Beat the egg and egg yolks in a medium bowl with a fork or whisk.

Stir 8 tablespoons sugar and the cornstarch in a 1-quart saucepan. Add the milk and stir until the mixture is smooth. Cook and stir over medium heat until the mixture boils and thickens. Remove the saucepan from the heat. Gradually stir half the milk mixture into the eggs. Return the egg mixture to the saucepan. Cook and stir over medium heat for 1 minute. Remove the saucepan from the heat. Stir in the butter. Place plastic wrap directly onto the surface of the pastry cream and refrigerate for 30 minutes

Beat the heavy cream, 1/2 cup cocoa powder and remaining sugar in a large bowl with an electric mixer on high speed until stiff peaks form. Fold the pastry cream into the whipped cream mixture. Cover and refrigerate for 1 hour or until the mixture is well chilled.

Unfold the pastry sheet on a lightly floured surface. Roll the pastry sheet into a 12-inch square. Cut into 15 (3-inch) circles. Place the pastry circles onto 2 baking sheets.

Bake for 15 minutes or until the pastries are golden brown. Remove the pastries from the baking sheets and let cool on wire racks for 10 minutes. Split each pastry into 2 layers, making 30 in all.

Reserve 10 pastry tops. Spoon about 2 tablespoons cream mixture and 1 to 2 cherries onto each of 10 remaining pastry layers. Repeat the layers and top with the reserved pastry tops. Sprinkle with additional cocoa powder.

For Brandied Bing Cherries: Drain the liquid from 1 jar (21 ounces) cherry pie filling. Add brandy to taste.