Let the pears soak for several hours the day before for an extra-flavorful dessert.
For the crusts, in a food processor, pulse the flour, sugar, and salt. Add the butter; pulse until chickpea-size pieces form, about 6 times. In a small bowl, mix the ice water and vinegar. Pour over the flour; pulse until moist clumps form. Transfer the dough to a work surface. Knead a few times to bring the dough together; divide into 2 equal portions. Roll the dough into balls; flatten into disks. Wrap in plastic; refrigerate for 1 hour.
For the filling, in a large pan, bring the wine, 1 cup sugar, the fennel seeds, and peppercorns to a boil, stirring to dissolve the sugar. Add the pears; return to a boil. Reduce heat to medium and simmer, stirring occasionally, until the pears are tender, 10 to 15 minutes. Using a slotted spoon, transfer the pears to a bowl, brushing off any spices that may be clinging to the pears. Strain the syrup into a large bowl. Let cool to room temperature, about 30 minutes. Add the pears to the syrup. Cover and refrigerate for at least 12 hours.
On a lightly floured work surface, roll out 1 disk of dough into a 12- to 13-inch round. Transfer to a 9-inch pie dish, fitting the dough into the edges. Crimp the edges decoratively. Roll out the remaining dough into a 12- to 13-inch round. Using a plate or the bottom of a tart pan with a removable bottom, cut the pastry into a 9-inch circle for the top crust. Using cookie cutters, cut out shapes in the top crust in a decorative pattern. Transfer the top crust to a baking sheet. Cover and refrigerate both crusts until firm, about 1 hour.
Preheat the oven to 400°. Using a slotted spoon, transfer the pears to a medium bowl. Mix in 1/4 cup of the syrup. (Reserve the remaining syrup to make flavored sodas or cocktails.) In a small bowl, whisk 1/4 cup sugar and the cornstarch. Add to the pears; toss until coated. Transfer to the pie dish. Place the top crust on top of the pears. Brush with the beaten egg. Sprinkle with the remaining 1 tbsp. sugar.
Bake the pie until the filling is bubbling and the top is golden brown, rotating the dish halfway through baking for even cooking and tenting the top with foil if it browns too quickly, about 1 hour, 15 minutes. Let cool on a wire rack for 45 minutes to 1 hour. Serve the pie with ice cream.
Up To 2 Months Ahead: Make the dough. Store in an airtight container in the freezer. Thaw overnight in the refrigerator before rolling.
1 Day Ahead: Poach the pears. Store the pears in the syrup in the fridge. Roll out and prepare the crusts. Cover and refrigerate both crusts.
8 Hours Ahead: Bake the pie. Let stand at room temperature.
Thanksgiving recipes for planners and procrastinators here.