In a small saucepan, heat 1 cup (240 grams) cream and 1 tablespoon (12 grams) sugar over medium heat, stirring occasionally, until steaming and sugar dissolves. (Do not boil.)
In a medium bowl, whisk together egg yolks and remaining 1 tablespoon (12 grams) sugar. Slowly pour hot cream mixture into yolk mixture, whisking constantly. Return mixture to saucepan, and cook over medium heat until an instant-read thermometer registers 180°F (82°C). Using a fine-mesh sieve, strain hot cream mixture over chocolate, and let stand for 5 minutes. Whisk until chocolate is melted and mixture is smooth and shiny.
In the bowl of a stand mixer fitted with the whisk attachment, beat remaining 2 cups (480 grams) cream at high speed until soft peaks form. Fold whipped cream into chocolate mixture until combined. Spoon filling into Honey Graham Cereal Piecrust. Refrigerate for 2 hours or up to overnight.
Spoon Whipped Chocolate Topping into a pastry bag fitted with a 1⁄2-inch French star piping tip (Ateco #869). Pipe around edges of pie. Garnish with cereal, if desired.