Step 1: Prepare the Crust

1. Preheat your oven to 350°F (175°C).
2. In a bowl, mix the chocolate cookie crumbs and melted butter until evenly coated.
3. Press the mixture firmly into the bottom and sides of a 9-inch pie dish.
4. Bake for 8-10 minutes, then let it cool completely.

Step 2: Make the Filling

1. In a saucepan over medium heat, melt the sugar, butter, and unsweetened chocolate, stirring until smooth. Remove from heat.
2. In a mixing bowl, whisk the eggs and vanilla extract. Slowly add the chocolate mixture, whisking constantly to prevent the eggs from scrambling.
3. Stir in the flour until fully incorporated.
4. Pour the filling into the cooled crust.
5. Bake for 25-30 minutes or until the filling is set and slightly cracked on top. Cool completely before adding the topping.

Step 3: Whip the Topping

1. In a chilled bowl, whip the heavy cream, powdered sugar, and vanilla extract until soft peaks form.
2. Spread the whipped cream evenly over the cooled pie.

Step 4: Garnish and Serve

1. Sprinkle chocolate shavings or drizzle chocolate syrup over the top for decoration.
2. Chill the pie in the refrigerator for at least 2 hours before serving.