Stir together flour, brown sugar, pumpkin pie spice, cream of tartar, baking soda, and salt in a medium mixing bowl.
Using a grater, shred the butter. Mix the shredded butter into the dry mixture using a fork, pastry blender, or your fingers. (OR, Cut the butter into ¼ cubes and blend together.)The mixture should look like very coarse crumbs.
In a separate bowl, mix sourdough starter, pumpkin, molasses, orange zest, and vanilla.
Stir wet mixture into dry mixture in the bowl. Once it is somewhat mixed in, turn the contents of the bowl out onto a clean board. The mix may seem a little dry at first. Knead it a few times before you decide to add milk.
Gently knead the dough on the board, adding milk if necessary, just until it holds together in a soft ball. The dough should soft like a biscuit dough. Once you've kneaded it enough for it to pull together, Just form a ball and leave it alone. The less you work with it, the tenderer your scones will turn out. Allow the dough to rest for 5 minutes.
Form a 9-inch wheel with the dough dough.
Transfer the wheel of dough to the prepared baking sheet. With a long knife, cut the dough wheel into eight pieces, like a pizza. Separate pieces so that they are ½-inch away from one another.
Brush the top of the wheel with milk.
Put the scones on the baking sheet in the freezer.Set your oven to 400°F [204°C].
When the oven is fully up to temperature, take the scones out of the freezer. Put the scones into the oven and bake for 20-25 minutes.
Remove from oven and cool on wire rack for 15 minutes.
In a small mixing bowl, combine Pumpkin Spice Glaze ingredients. Mix until smooth.
Drizzle the glaze over the scones.
Notes
SOURDOUGH STARTER: Use Sourdough Discard or Unfed Starter for this recipe.
Discard should must be from a healthy, vigorous Starter that is regularly fed.
Unfed Starter should be healthy, vigorous sourdough starter that has not been fed for 12 hours or more. (DO NOT use neglected Starter that hasn’t been fed in weeks.)
PUMPKIN: You can use home-cooked pumpkin, but you may need to add a little milk or extra flour to the mix to adjust for the difference in moisture content.