1. Preheat the oven to 375°F (190°C) if baking a homemade crust. Bake the pie crust until golden brown and allow it to cool completely.

2. In a medium saucepan, whisk together the sugar, cornstarch, and salt until evenly combined.

3. In a separate bowl, whisk the egg yolks lightly. Gradually whisk the milk into the dry ingredients, then add the egg yolks.

4. Place the saucepan over medium heat and cook while whisking constantly until the mixture thickens and begins bubbling gently.

5. Remove the saucepan from the heat and stir in the chopped chocolate until melted and smooth.

6. Add the butter, vanilla extract, and optional espresso powder. Stir until glossy and fully combined.

7. Pour the chocolate filling into the cooled pie crust and smooth the top with a spatula.

8. Press plastic wrap directly onto the surface of the filling and refrigerate for at least 4 to 6 hours or overnight.

9. In a chilled mixing bowl, beat the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.

10. Spread or pipe the whipped cream over the chilled pie.

11. Garnish with chocolate curls, chocolate shavings, cocoa powder, or mini chocolate chips.

12. Slice and serve chilled.