• Preheat oven to 400 degrees F. Prepare a baking sheet with a silicone baking mat or parchment paper.
• Starting with the dry ingredients first. In a large mixing bowl, sift and combine the flour, baking powder, baking soda, brown sugar, salt, and pumpkin spice.  Set aside.
• Next, separate the egg yolk from the white.  Save the yolk for the last step before baking.
• In another bowl, whisk together the egg white, butter, sour cream, and molasses. 
• Once completely mixed through, add the dry ingredients. Beat in the dry ingredients in until just combined. Don’t overmix – the dough will form quite quickly and shouldn’t be one complete, perfectly round ball of dough.
• Turn the dough out onto a lightly floured surface. Use your hands to push the dough together, gathering up the bits into a mound. Sprinkle the top lightly with flour and push the dough into a round shape about 1 inch thick. Use a knife to cut the dough into 8 wedges. Transfer those to the baking sheet.
• Use a pastry brush to dust off any excess flour. 
• Add one tablespoon of water to the reserved egg yolk and whisk to combine.  Using a pastry brush, lightly brush the top of each scone with the egg yolk mixture.
• Sprinkle over the sanding sugar, if using. 
• Bake for 13 minutes depending on your oven, until the top is just slightly golden in colour. Remove from oven and transfer to a wire cooling rack immediately.

For the Optional Glaze:

• Whisk together 1 1/2 cups of confectioners sugar with 2 tablespoons of milk. (You can use more or less milk depending on how thick or thin you would like the glaze.) Drizzle the glaze over the completely cooled scones. Serve immediately or allow the glaze to firm before packing the scones into a food-safe container.