1. Position a rack in the center of your oven and preheat the oven to 375°F. Wrap each kabocha squash half tightly in aluminum foil and bake until you can easily stick a fork into the squash, about 40 minutes. Unwrap the kabocha squash and let it cool completely. Scrape the orange flesh from the squash and discard the peel. Leave the oven on.
2. Remove the pie dough from fridge and remove the plastic wrap. If your dough has been chilled overnight, it will need to sit at room temperature for a bit before rolling—this will take 10 to 15 minutes. Lightly flour your work surface and roll the pie dough out to a 13-inch round that is 8 inches thick. Transfer to a 91⁄2-inch pie dish and use your fingertips to relax the dough into the shape of the pie dish, leaving a 2-inch overhang around the edge of the dish. Fold the extra dough under itself. Use your thumb and forefinger to crimp the edge of the dough, pressing the dough into the pie dish and making sure the dough extends to the outer edge of the dish. This anchors the crust inside the dish, which results in a proud crown of crust after baking. Freeze the crimped crust for about 20 minutes, until the dough is very cold.
3. Line the crust with heavy-duty foil, leaving an 11⁄2-inch overhang. Trace your fingertips over the foil overhang and gently press it into the crimp. Fill the foil-lined crust with pie weights or dried beans. Bake for 20 to 25 minutes, until the crust is golden around the edges. Remove from the oven and lift out the foil and pie weights. Cool the crust completely.
4. Reduce the oven temperature to 325°F.
5. Put the maple syrup into a medium saucepan and bring it to a rolling boil over medium heat. Cook the maple syrup until a candy thermometer registers 235°F, about 10 minutes. Remove the pan from the heat and add the heavy cream and salt. Place the pan back on the stove over medium heat and bring it to a simmer. Remove from the heat and let cool for 15 minutes.
6. Combine the kabocha squash, eggs, cinnamon, and nutmeg in the carafe of a blender. Blend on high until very smooth. Reduce speed to low and slowly stream in the maple caramel. Blend until combined.
7. Pour the filling into prepared crust and bake the pie until the center of the custard wobbles a bit when the pie is gently jiggled, about 40 minutes. Cool the pie on a wire rack for 1 hour before serving. Serve the pie dolloped with whipped cream if you desire. Store leftovers in the fridge for up to 1 week.
FLAKY BUTTER CRUST
Makes two 9½-inch single crusts or 1 double crust with some dough left over for lattice work or other decoration.
1. In a measuring cup, combine the brown sugar, vinegar, and salt with ¾ cup (107ml) of hot water. Stir until the sugar has dissolved. Chill the liquid in the freezer until it is very cold (this should take about 20 minutes) and leave it in the fridge until you are ready to start the rest of the dough.
2. Combine the flour and half of the butter in a large mixing bowl. Pinch and smear the butter between your fingers. Processing the butter like this creates small leaves of butter that layer in the dough, resulting in flakes later. Once all the butter chunks have been pinched, grab small handfuls of flour and butter and rub the two together between the palms of your hands until mixture resembles uneven pebbles on a sandy beach.
3. Dump the crumbly mixture out onto a lightly floured work surface. Scatter the remaining half of the cold butter over the dough. Use the palm of your hand to smear the butter as if you were sliding a secret message across a table. Use a bench scraper to gather the shaggy dough and repeat the smearing process until you have a pile of striated rubble. The larger pieces of butter will create a marbled dough and will melt during baking, causing the water in the butter to evaporate (this will result in flaky pastry pockets).
4. Gather the buttery mixture up in a mound and form a well in the center. Remove the cold liquid from the fridge and pour half of it into the well. Using your fingertips, slowly bring the flour and butter into the center and combine it with the liquid, until the liquid has been incorporated. Gather the moistened dough into a pile.
5. Slowly pour the remaining liquid onto the shaggy mess. Lift the dough from the bottom and squeeze just until it comes together into one mass. Divide the ball in half and shape each half into a disc. Wrap each in plastic and chill for 2 hours before using.