1. Bake the pie crust if needed, then let it cool completely before adding the filling.

2. In a medium saucepan, whisk together the granulated sugar, cocoa powder, cornstarch, and salt.

3. Slowly whisk in the whole milk until smooth, then add the egg yolks and whisk until fully combined.

4. Set the saucepan over medium heat and cook, whisking constantly, until the mixture thickens and begins to bubble.

5. Remove the pan from the heat and stir in the semi sweet chocolate, unsalted butter, and vanilla extract until smooth and glossy.

6. Pour the chocolate filling into the cooled pie crust and smooth the top evenly.

7. Press plastic wrap directly onto the surface of the filling and refrigerate for at least 4 hours, or until fully set.

8. Beat the heavy whipping cream with the powdered sugar until soft to medium peaks form.

9. Spoon or pipe the whipped cream over the chilled pie.

10. Finish with chocolate shavings or chocolate curls before slicing and serving.