Preheat the oven to 400F. Line a baking sheet with parchment paper.
In a large bowl, whisk the flour, baking powder, cinnamon, pumpkin pie spice, and salt together until well incorporated.
Grate the frozen butter using a cheese box grater.
Mix the grated butter into the dry ingredients from step two using your hands until the mixture comes together with small butter crumbs.
In a large measuring cup, whisk 1/3 cup heavy cream, egg, pumpkin puree, brown sugar, and vanilla together until smooth. Pour this mixture into the flour/butter bowl then mix until a dough ball forms.
Lay the dough ball out on a floured work surface then form it into a disc, about 8 inches in diameter, then slice it into 8 equal-sized wedges.
Arrange scones on the prepared baking sheet then brush the remaining 2 tbsps of heavy cream on top of each scone.
Bake for 25-30 minutes or until golden. Remove the scones from the oven and allow to cool before adding glaze.
While the scones bake, make your glaze: Whisk together all glaze ingredients in a small bowl until smooth.
Once scones have cooled slightly, drizzle glaze over top then enjoy!