In a large mixing bowl, combine all-purpose flour and kosher salt. Cut in unsalted butter until the mixture resembles coarse crumbs. Gradually add ice-cold water until the dough comes together. Wrap and chill for 1-2 hours.

Preheat your oven to 375°F (190°C). Roll out the dough into a circle about 12 inches in diameter. Transfer to a 9-inch pie plate, freeze for 15 minutes, then dock the bottom, fill with weights, and bake for 15 minutes. Remove weights and bake for another 5 minutes.

In a mixing bowl, whisk together the apple butter, large eggs, dark brown sugar, and all-purpose flour until well combined. Gradually stir in sweetened condensed milk and vanilla extract until smooth.

Pour the filling into the par-baked crust and bake at 325°F (160°C) for 30 minutes. Check and bake for an additional 10-15 minutes until the filling is set but slightly jiggly in the center.

Remove from the oven and let cool at room temperature for about 3 hours. Optionally refrigerate for an hour.

For the whipped cream, combine heavy whipping cream, powdered sugar, ground cinnamon, and vanilla extract in a chilled mixing bowl. Beat until soft-stiff peaks form.

Slice your pie and serve immediately, topping each slice with whipped cream. Optionally drizzle with apple butter.