In a large mixing bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger.
Add the cold butter cubes and cut into the mixture using a pastry cutter or two butter knives until the largest pieces are the size of peas; set aside.
In a separate smaller bowl, whisk together the pumpkin puree, brown sugar, egg, and heavy cream until well combined.
Add the wet ingredients to the flour mixture and stir until just combined. The dough will be very wet and sticky.
Transfer the dough to a well-floured surface, sprinkle some flour on top, and form an 8-inch (20 cm) disc using floured hands. Cut the scones using a sharp knife into 8 equal wedges, then carefully transfer them to a parchment-lined baking sheet.
Preheat the oven to 400°F (200°C), or 180°C if using a fan oven. While the oven preheats, chill the scones in the fridge.
Remove from the fridge then brush with a little heavy cream before baking in the preheated oven for 12 to 15 minutes, or until a toothpick inserted into the center comes out clean and the bottom is just lightly golden.
While the scones bake, prepare the glaze by whisking together 2 cups of the powdered sugar and heavy cream until smooth and spreadable.
Allow the scones to cool completely before spooning and spreading the glaze over the top of each scone.
To the remaining glaze in the bowl, whisk in the pumpkin puree and cinnamon until smooth. If the icing is too thin, add a sprinkle of powdered sugar until it is the desired consistency.
Drizzle or pipe the pumpkin glaze over the scones once the first layer has set slightly, about 10 minutes.
