Cut the butter into cubes and put it into the freezer.
Combine the flour, brown sugar, baking powder, pumpkin pie spice, cinnamon and salt together in a large mixing bowl. Sir to mix.
In a small mixing bowl, whisk together the egg, pumpkin puree, sourdough starter, heavy cream and vanilla extract.
Cut the cold butter into the dry ingredients with a pastry blender until the butter resembles small peas.
Add the wet ingredients to the dry ones in the large bowl. Mix together with a spoon in the large bowl. Mix with a spoon and then knead the ingredients together with your hands just until the dough forms into a ball. Do not over-knead the dough. The less it is handled the better.
Turn the dough out on a work surface or a dinner plate, and press into a disk about one inch thick. Cut the disk into eight wedges.
Preheat the oven to 400 degrees F. Put the dough into the fridge for 10 to 15 minutes while the oven heats up. Line a baking sheet with parchment paper.
When the oven is heated, remove the dough from the fridge and place it on prepared baking sheet, with the scones not touching each other. Bake for 20-25 minutes or until lightly browned. Remove from oven and allow to cool on a wire rack.
While scones are cooling, make the glaze. Mix all of the glaze ingredients together in a small bowl. Drizzle glaze over the cooled scones.
Notes
You can double the maple glaze ingredients if you prefer more of a completely frosted scone. The recipe I've included will make a glaze that you can drizzle over the scones, but it could be easily doubled.
Be sure to use very cold butter in this recipe. I like to cut my butter into small cubes and then put it into the freezer while I get out the other ingredients and get everything ready.