Preheat the oven to 350°F (175°C).

Prepare the pie crust by gently poking holes in it with a fork. Bake it for about 20 minutes until lightly golden brown, then let it cool completely.

Whisk together the all-purpose flour, cocoa powder, sugar, salt, egg yolks, and whole milk in a saucepan.

Cook over medium heat, stirring constantly for about 5–10 minutes until the mixture thickens to a pudding-like consistency.

Remove from heat, then stir in the unsalted butter and vanilla extract until fully combined.

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

Chill your pie in the refrigerator for at least 4 hours, or overnight for best results.

Serve the pie chilled, generously topped with whipped cream.