Reduce the oven temperature to 350 degrees F and continue baking until the crust is golden and the filling is bubbly in spots, about 55 more minutes (the center will still jiggle slightly) cover the crust edges with foil if they're browning too quickly. Carefully transfer the pie plate to the hot baking sheet and bake 10 minutes. Pour into the chilled crust, dot with the butter and sprinkle the nutmeg on top. Make the filling: Whisk the heavy whipping cream, sugar, flour and vanilla in a bowl. Pour in heavy cream and mix together until fully blended and incorporated. Combine sugar, flour, nutmeg and salt in a large bowl and whisk together. Place a baking sheet on the middle oven rack and preheat to 425 degrees F. Preheat oven to 350 F and place pie dough in a standard pie dish. Refrigerate the crust until firm, about 30 minutes. Fold the overhanging dough under itself and crimp the edges with your fingers. Roll out the dough into an 11-inch round on a lightly floured surface. Turn out onto a sheet of plastic wrap and pat into a disk wrap tightly and refrigerate at least 1 hour and up to 1 day. Drizzle in 3 tablespoons ice water and pulse until the dough begins to come together (add more water, 1/2 tablespoon at a time, if necessary). Because pie pan depths may vary, keep in mind that this filling is supposed to come almost up to the top of the pie. Distribute filling evenly over shortbread in the prepared pan. Add the butter and shortening and pulse until the mixture looks like coarse meal with pea-size bits of butter. Place prepared pie pan on a cookie sheet (in case of any overflow during baking).
Make the crust: Pulse the flour and salt in a food processor. Sugar cream pie is a single-crust pie with a smooth filling made from flour, butter, salt, vanilla, cream, and brown sugar.