Cook over medium heat, stirring frequently at first, then constantly as mixture starts to thicken and begins to simmer, 8 to 10 minutes. Once mixture simmers, continue to cook, stirring constantly, for 1 minute longer. Remove pan from heat; whisk in butter, chocolate and brandy.
Pour filling into shallow pan (another pie pan works well). Put plastic wrap directly over filling surface to prevent skin from forming; cool until warm, about 30 minutes. Pour warm filling into pie shell and, once again, place sheet of plastic wrap directly over filling surface. Refrigerate pie until completely chilled, at least 3 hours.
Whip cream to soft peaks. Add powdered sugar and vanilla; continue to whip to barely stiff peaks. Spread over filling and refrigerate until ready to serve.
Nutrition information per serving:
Calories515Cholesterol180 mg
Carbohydrates53 gSodium190 mg