Place the butter for the pie crust in the freezer for about 10 minutes before beginning. In a large bowl, whisk together the flour, granulated sugar, and table salt.

Slice or grate the cold butter into thin pieces. Add about 1 tablespoon (14 g) of the butter to the flour mixture and rub it in with your fingertips until evenly distributed and the mixture resembles fine breadcrumbs.

Add the remaining cold butter. Use your fingers to press and flatten the butter into the flour, leaving visible pieces about the size of sliced almonds. The mixture should look shaggy, with flattened pieces of butter throughout and no large areas of dry flour.

Sprinkle the ice-cold water over the mixture, about 1 tablespoon (15 ml) at a time, gently tossing with a fork after each addition. Stop adding water as soon as the dough forms clumps that stay together when squeezed. You may not need the full amount.

Transfer the dough to a work surface and gently press it together with your hands without kneading. Shape into a thick disc, wrap tightly, and refrigerate for at least 2 hours or overnight.

Once the dough has chilled, roll it on a lightly floured surface into a circle large enough to fit a 9-inch (23 cm) pie plate with approximately 1½–2 inches (4–5 cm) of overhang. Keep the thickness as even as possible so the crust bakes consistently.

Transfer the dough to the pie plate without stretching it. Trim the excess dough, fold the overhang underneath itself, and crimp the edge as desired. Refrigerate the fitted crust for at least 30 minutes while preparing the filling.

If using refrigerated pie dough, fit it into a 9-inch (23 cm) pie plate, crimp the edge, and refrigerate for at least 30 minutes before filling. If using a frozen pie shell, keep it frozen until the filling is ready and follow the package instructions. Do not prebake the crust unless directed by the manufacturer.

While the crust chills, preheat the oven to 350°F (175°C). Spread all 2 cups (200 g) of pecan halves in a single layer on a baking sheet. Toast for 7–9 minutes, stirring once, until fragrant and slightly darker in color. Watch closely toward the end of the baking time to prevent burning.

Allow the pecans to cool completely. Reserve approximately ½ cup (50 g) of the whole pecan halves for decorating the top of the pie and roughly chop the remaining 1½ cups (150 g) for the filling.

Carefully add the dark brown sugar and pure maple syrup, stirring to combine. Return the saucepan to medium-low heat and cook, stirring frequently, until the mixture is smooth and the sugar is well incorporated. Bring to a gentle simmer, then remove from the heat.

Allow the maple mixture to cool for approximately 15 minutes, until still fluid and warm but no longer very hot. The mixture needs to cool enough that it won't scramble the eggs when they are added.

In a separate bowl, whisk the eggs until the yolks and whites are completely combined. Slowly whisk approximately ½ cup (120 ml) of the warm maple mixture into the eggs, adding it gradually while whisking continuously to temper them.

Gradually whisk the tempered eggs back into the saucepan with the remaining maple mixture until thoroughly combined. Whisk in the bourbon, vanilla extract, and kosher salt, then fold in the chopped toasted pecans.

When the filling is ready, increase the oven temperature to 425°F (220°C). Place the chilled pie crust on a rimmed baking sheet to catch any filling that may bubble over during baking.

In a small bowl, whisk together the egg yolk and milk or water. Lightly brush the exposed crimped edge of the pastry with the egg wash, taking care not to let it collect in the folds.

Pour the filling into the cold pie shell and arrange the reserved toasted pecan halves over the surface in your desired pattern. Transfer the pie to the oven immediately while the pastry is still cold.

Bake at 425°F (220°C) for 10–12 minutes. Without removing the pie from the oven, reduce the temperature to 350°F (175°C) and continue baking for 35–45 minutes, checking toward the beginning of that range.

Watch the exposed pastry as the pie bakes. Once the crimped edge becomes deeply golden, loosely cover it with aluminum foil or a pie shield to prevent excessive browning while the filling finishes baking.

The pie is ready when the filling around the outside is set and slightly puffed, while the center still has a gentle jiggle when the pie is carefully nudged. The center should move slightly as one mass rather than appearing liquid. Do not wait until the entire filling is completely firm because it will continue setting as the pie cools.

Transfer the baked pie to a wire rack and sprinkle the surface lightly with flaky sea salt while the filling is still warm. Allow the pie to cool completely for at least 3 hours before slicing so the filling has enough time to set.

Serve at room temperature or slightly warmed, with whipped cream or vanilla ice cream if desired.