Add ¾ cups of all-purpose flour and ½ tsp of salt to a large food processor and pulse together 2 to 3 times.
Scatter ½ cup of cold unsalted butter over the flour and process until a crumbly dough forms, about 15 seconds. The flour should be fully coated.
Add the remaining ½ cup of flour and pulse a few times until evenly distributed; the mixture should resemble sand.
Move the mixture to a medium mixing bowl and add 2 tablespoons of very cold water. Gently fold together until larger clusters form. Add more water as needed.
Pour the dough out onto parchment paper, shape into a disc, and refrigerate for at least one hour.
Preheat oven to 350°F (180°C). Roll out the dough and transfer it into a pie plate.
Chill the crust in the freezer for 10 to 15 minutes, then line with parchment paper and fill with weights.
Bake for 20 to 25 minutes or until edges are lightly golden. Remove weights and set aside.
In a large bowl, combine 1 ¾ cups of sugar, 4 tablespoons of cocoa powder, and 4 tablespoons of cornstarch. Set aside.
Melt 4 tablespoons of unsalted butter in the microwave with a splash of whole milk.
In another bowl, whisk together 3 large eggs, the melted butter, milk, and 1 teaspoon of vanilla extract.
Combine wet and dry ingredients, stirring gently until well blended.
Pour the filling into the baked crust and bake for 50 to 60 minutes until set and a crust forms.
Allow the pie to cool to room temperature before serving.
