In a large bowl, mix the brown sugar, lemon juice, ground cinnamon, ground ginger, kosher salt, and ground nutmeg until combined. Peel, core, and slice the Granny Smith apples, then toss them in the sugar mixture to coat. Let the mixture sit at room temperature for 3-4 hours.

Roll out the pie dough into a 12-inch circle on a lightly floured surface. Fit the rolled dough into a 9-inch pie plate and trim any excess around the edges, crimping them for a decorative touch. Chill the crust for at least 1 hour.

In a medium bowl, combine all-purpose flour, chopped walnuts (if using), brown sugar, and salt. Pour in the melted butter and mix until the mixture resembles coarse crumbs. Chill the streusel topping in the refrigerator until firm, about 30 minutes.

After the apple mixture has rested, strain the apples to reduce excess juice if necessary. Layer the apple slices evenly in the prepared crust. Drizzle the heavy cream over the apples, then sprinkle the chilled streusel mixture evenly over the top.

Preheat your oven to 425°F (220°C). Place the assembled pie on the lowest rack and bake for 20 minutes. Lower the temperature to 375°F (190°C) and continue baking for 60-75 minutes until the crust is golden brown and the filling is bubbling.

Remove the pie from the oven and let it cool at room temperature for at least 4 hours for the filling to set.