Preheat the oven to 375°F (190°C) and line a baking sheet with parchment paper.

In a large bowl, whisk together the flour, sugar, baking powder, salt, and 2 teaspoons of the pumpkin pie spice. Add the cubed cold butter, using a pastry blender or two forks to cut it into the flour mixture until the texture resembles coarse crumbs.

In a separate bowl, combine the pumpkin puree, 6 tablespoons of heavy cream, the beaten egg, and 1 teaspoon of vanilla extract. Gradually add this mixture to the dry ingredients, stirring with a fork until just combined and a rough dough forms. If the dough seems too dry, add an extra tablespoon of cream.

Turn the dough out onto a lightly floured surface and knead gently until it comes together. Flatten the dough into a 1-inch thick circle and cut it into 12 wedges. Place the wedges on the prepared baking sheet and refrigerate for 30 minutes.

After chilling, brush the tops of the scones with the remaining 1 tablespoon of heavy cream and sprinkle with the remaining ½ teaspoon of pumpkin pie spice. Bake for 25 minutes, or until the tops are golden brown. Let cool for 5 minutes on the baking sheet, then transfer to a wire rack to cool completely.

While the scones cool, prepare the glaze. In a medium bowl, whisk together the confectioners' sugar, the remaining 6 tablespoons of heavy cream, and the remaining 1 teaspoon of vanilla extract until smooth. If the glaze is too thick, add more cream, a little at a time.

Drizzle the glaze over the cooled scones and let it set for about 10 minutes before serving.