Measure and divide the flour: set aside 3/4 cup (98 g) of the 1 1/4 cups (163 g) all-purpose flour and keep the remaining 1/2 cup (65 g) separate. Combine the 3/4 cup (98 g) flour and 1/2 teaspoon salt in a large food processor and pulse 2–3 times to mix.

Scatter the 1/2-inch cubes of 1/2 cup (112 g) cold unsalted butter over the flour in the processor. Pulse and then process in short bursts (about 15 seconds total) until the mixture is crumbly and all the flour is coated. The texture should be sandy with no large dry pockets of flour.

Add the remaining 1/2 cup (65 g) flour to the processor and pulse a few more times until the mixture looks evenly distributed and mostly sandy. A few slightly larger pieces are okay.

Transfer the mixture to a medium mixing bowl. Add 2 tablespoons of very cold water and gently fold with a rubber spatula until the crumbs begin to clump. Pinch a small amount—if it holds together when pressed, stop; if it falls apart, add up to 1–2 more tablespoons of very cold water (total 3–4 tbsp) until the dough just holds together when squeezed.

Turn the dough out onto a piece of parchment, work it just enough to form a single ball, then flatten into a disc. Wrap the disc tightly in plastic wrap and refrigerate for at least 1 hour or up to 2 days.

When ready to bake, place the chilled dough disc between two sheets of parchment paper (lightly floured if you like) and roll it into a circle large enough to fit a standard pie plate. Peel off the top sheet of parchment, flip the dough into the pie plate using the remaining parchment to help, and gently press the dough into the plate. Trim and crimp the edges as desired.

Put the shaped pie crust in the freezer for 10–15 minutes to firm up while you preheat the oven to 350°F (180°C).

Remove the crust from the freezer. Line the crust with a piece of parchment paper pressed flush against the dough, then fill with pie weights, dried beans, or rice to weigh it down.

Bake the crust (blind bake) at 350°F (180°C) for 20–25 minutes, or until the edges just begin to brown. Remove from the oven, carefully lift out the parchment and weights, and set the crust aside while you make the filling.

In a large bowl, whisk together 1 3/4 cups (362 g) sugar, 4 tablespoons (29 g) sifted cocoa powder, and 4 tablespoons (32 g) cornstarch until evenly combined.

In a small microwave-safe bowl, melt the 4 tablespoons (56 g) unsalted butter—heat in short bursts and watch closely so it does not burn. In a separate medium bowl, beat the 3 large eggs, then add the melted butter, 2/3 cup (160 ml) whole milk, and 1 teaspoon vanilla extract; whisk until smooth and well combined.

Pour the wet mixture into the dry mixture and gently stir until smooth and fully combined.

Pour the filling into the hot partially baked crust. Return the pie to the oven and bake at 350°F (180°C) for 50–60 minutes (about 55 minutes is typical), until a crust has formed on top and the filling is set—there may be a slight jiggle in the center but it should not be liquid. If the crust starts to brown too much, add a pie shield or foil around the edges about halfway through baking.

Remove the pie from the oven and let it cool completely to room temperature on a wire rack. Serve at room temperature or refrigerate until ready to serve.