Combine flour, salt, and sugar in a large bowl. Add the cold, cubed butter and use a pastry cutter or your fingertips to work it into the flour until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
Drizzle in ice water one tablespoon at a time, stirring gently with a fork until the dough just comes together. Shape into a disk, wrap in plastic, and refrigerate for at least 30 minutes.
While the dough chills, whisk together the pumpkin puree, heavy cream, brown sugar, eggs, vanilla, and spices in a medium bowl until smooth and well combined.
Preheat your oven to 375°F (190°C). On a lightly floured parchment paper, roll the chilled dough into a rough 12-13 inch circle about ⅛ inch thick.
Transfer the parchment with the dough onto a baking sheet. Pour the pumpkin filling into the center of the rolled dough, leaving about a 2-inch border all around.
Gently fold the edges of the dough over the filling, pleating as you go. The center will remain open, showcasing the filling.
Brush the folded dough edges with beaten egg and sprinkle with turbinado sugar.
Bake in the preheated oven for 45-50 minutes, until the crust is golden brown and the filling is set but still has a slight jiggle in the center. If the crust begins to brown too quickly, tent the edges with foil.
Allow the pie to cool completely on the baking sheet for at least 2 hours before serving.