1. Prepare your favorite 9-inch pie crust and blind bake it. Cool completely.

For the chocolate custard: 

1. Prepare all the ingredients prior to starting. In a medium saucepan, combine the flour, sugar, and cocoa powder and whisk together. Heat for 2 minutes on medium to medium-low heat, whisking occasionally.
2. Next, slowly whisk in the milk, pressing the whisk into the bottom edges of the saucepan to break up any clumps.
3. Continue whisking the custard until it starts to thicken and lightly bubble, approximately 10-15 minutes. The mixture will start to coat the outside of the pan as it thickens. Ensure it’s thicken before moving onto the next step.
4. Then slowly add the chopped chocolate and continue whisking until the chocolate is completely incorporated. Cook for 2-5 minutes, ensuring the custard is bubbling and thick, stirring occasionally.
5. Remove the custard from the heat and whisk in the vanilla extract and butter and whisk until the butter is melted and combined.
6. Strain the custard through a fine sieve, three times, rinsing the sieve in between each time.
7. Pour the custard into a heat proof bowl and cover with clear plastic wrap (placing directly on the surface of the custard), then poke a few holes in the plastic wrap with a toothpick.
8. Allow the custard to cool on the counter for at least 1 hour before refrigerating.
9. Refrigerate 2-4 hours until the custard has cooled and is firm. Pour in the prepared pie crust. Prepare the whipped cream prior to serving.

For the whipped cream:

1. Prepare the whipped cream. Place the mixing bowl and whisk attachment in the freezer for 5 to 10 minutes to chill. Pour the heavy whipping cream into the chilled bowl and use an electric mixer to beat the heavy cream on medium-high speed until soft peaks start to form. Slowly add the powdered sugar and continue beating on high speed until stiff peaks form. Top with chocolate shavings (optional) or dust with cocoa powder.

For the chocolate shavings:

1. Combine chocolate and shortening in a heat-proof bowl. Microwave at 50% power in 30-second increments until the chocolate is melted and stir until completely smooth.
2. Using an offset spatula to thinly spread the chocolate over a flat surface, such as a cookie sheet. Refrigerate until the chocolate is firm. Use a bench scraper or the offset spatula to scrape the chocolate off the sheet pan.