Prepare a baking tray with a silicone mat or non-stick parchment.
In a large bowl, whisk together the flour, pumpkin pie spice, baking powder, baking soda, and salt. Set aside.
In a separate bowl, whisk together the pumpkin puree, egg white, maple syrup, milk, and vanilla extract. Set aside.
Grate the cold butter into the large bowl of dry ingredients. Using a fork, crumble the butter gratings into the dry ingredients until all the larger pieces have broken down.
Pour the wet ingredients into the dry ingredients and bring together using the fork until all the flour disappears. This dough will be quite wet.
Dust a work surface with flour then scrape the dough out onto the floured surface. Dust your hands and the top of the scone dough with flour and then bring the dough together into a 15 cm (6 inch) diameter disc. Be very gentle with this dough and try to work it as little as possible.
Using a sharp knife, cut the dough evenly into 6 triangles. Gently place the scones on the prepared baking tray, spaced evenly apart. Refrigerate the scones for 30-60 minutes.
Preheat the oven to 190ºC (375ºF) and bake the scones for 14-16 minutes. They should be well-risen and golden brown all over.
Remove the scones from the oven and allow them to cool on the tray for 5 minutes, then place them on a wire rack to finish cooling.