In a food processor, pulse together the flour, sugar, and salt until combined. Add the chilled butter cubes and cold vegetable shortening, pulsing for 7-10 seconds until the mixture resembles coarse breadcrumbs with some pea-sized pieces of fat still visible—this creates the flaky layers we want. Add the remaining flour and pulse 4-6 times to distribute it evenly. Transfer the mixture to a bowl and stir in the vodka and water until the dough just comes together; don't overmix. I find vodka works better than water alone here because it evaporates faster during baking, resulting in a crispier crust.

Shape the dough into a disk, wrap it in plastic wrap, and refrigerate for at least 30 minutes (or up to overnight). On a floured surface, roll the chilled dough into a 12-inch circle about 1/8-inch thick. Transfer it to a 9-inch pie plate, letting the excess hang over the edges. Trim the overhang to about 1 inch, then fold it under and crimp the edges decoratively with a fork or your fingers. Chill the shaped crust in the freezer for at least 2 hours, or until very firm—this prevents shrinking during baking.

Preheat your oven to 350°F. Line the chilled crust with parchment paper or foil and fill it with pie weights, dried beans, or sugar to keep the bottom from puffing up. Bake for 40 minutes until the edges are set and lightly golden. Remove the foil and weights carefully, then set the crust aside to cool slightly. The crust doesn't need to be fully baked at this point—it will finish cooking when the filling bakes.

While the crust bakes, combine the melted butter, brown sugar, and granulated sugar in a large bowl. Add the eggs one at a time, whisking well after each addition to incorporate air and create a frothy, emulsified filling. Whisk in the bourbon, vanilla extract, and espresso powder until smooth and well combined. The espresso powder won't taste like coffee—it deepens the chocolate flavor instead. Fold in the coarsely chopped walnuts and semi-sweet chocolate chips along with the salt, stirring gently to distribute them evenly.

Pour the filling from Step 4 into the partially baked crust from Step 3. To prevent the edges from over-browning, cover the crust rim with a pie shield or a strip of aluminum foil. Bake at 350°F for 50-60 minutes, until the filling is mostly set but still slightly jiggly in the very center—it will continue to set as it cools. I always check for doneness by gently shaking the pie; if only the center wobbles slightly, it's done.

Remove the pie from the oven and let it cool to room temperature on a wire rack, about 1-2 hours. Transfer it to the refrigerator and chill for at least 4 hours (or overnight) before slicing. This resting time allows the filling to set completely and the flavors to meld beautifully. Serve slices at room temperature or slightly chilled with whipped cream or vanilla ice cream if desired.