In a large bowl, whisk together flour, baking powder, salt, spices, and sugar. Then use the side of a box grater with large holes to grate the butter. Add the butter to the flour mixture and toss the butter flakes, rubbing the butter into the flour a bit so they resemble the size of peas.
In a medium bowl, whisk together sourdough discard, egg, pumpkin, vanilla, and heavy cream until smooth. Pour liquid mixture over the dry, and gently use a spatula to combine just until no dry streaks remain.
Transfer the dough to a lightly floured surface, and knead until it comes together nicely, 6 to 8 times, adding flour as necessary as the dough will be a bit sticky.
Pat the dough into a small square with a dusting of flour on top and roll it into a 12-inch square. Transfer to a floured plate and freeze for 15 minutes.
Remove dough from freezer and fold the dough in thirds using a bench scraper, bringing the bottom towards the middle, then the top over it, like you would do when folding a business letter. Then fold the left side into the middle, and the right side over that to make a square. These are all your layers! Flip square over using a bench scraper, so seam of square is on the bottom. Roll dough out to a 12 x 4 inch long rectangle, using flour to keep it from sticking. Transfer dough back onto floured plate or baking sheet and freeze for 30 minutes, while oven is preheating to 400 degrees F.
Remove from freezer and use a 2 1/2 inch biscuit cutter to make 8 scones, pulling straight up on the biscuit cutter without twisting (this is to keep the super flaky layers). Or you can use a bench scraper (or sharp knife) to cut the rectangle crosswise into 4 equal rectangles, then cut each rectangle diagonally into 2 triangles.
Place scones onto parchment lined baking sheet. Brush the tops with a little heavy cream. Bake 20 to 22 minutes, rotating the pan halfway through, until the tops and bottoms are golden brown. Remove from oven and transfer scones to a cooling rack.
Whisk powdered sugar, heavy cream, maple syrup, and salt together until smooth. Glaze each scone and enjoy.