Freeze the unsalted butter for 10 minutes so it is very cold.

Combine 3 cups all-purpose flour, granulated sugar, and 1 teaspoon salt in a mixing bowl.

Grate the cold unsalted butter into the flour mixture using a box grater.

Rub the butter into the dry ingredients with your fingertips until coarse crumbs form.

Add 3 tablespoons ice water and mix until the dough starts to clump together.

Add the remaining ice water, 1 tablespoon at a time, until the dough holds together when squeezed.

Divide the dough into 2 equal portions and flatten each portion into a 1-inch-thick disk.

Wrap the dough disks and chill them in the refrigerator for 30 minutes.

Whisk pumpkin puree, egg, brown sugar, sour cream, cinnamon, nutmeg, ginger, and 1/2 teaspoon salt in a second mixing bowl.

Whisk 2 tablespoons all-purpose flour into the pumpkin filling until smooth.

Preheat the oven to 350°F (175°C) and line the baking sheet with parchment paper.

Roll one chilled dough disk on a lightly floured surface to 1/8-inch thickness.

Cut the rolled dough into 16 matching rounds using a round cookie cutter.

Cut 3 small vents into 8 dough rounds with a knife, leaving the other 8 rounds intact.

Spoon 1 1/2 tablespoons pumpkin filling onto the center of each intact dough round.

Place a vented dough round over each filled round and press the edges together.

Crimp the sealed edges with a fork without squeezing out the filling.

Arrange the pasties on the lined baking sheet and brush their tops with heavy cream.

Sprinkle cinnamon sugar over the cream-brushed pasties.

Bake the pasties for 20 to 25 minutes until golden brown.

Transfer the baked pasties to a wire cooling rack and cool before serving.