Start by measuring out the pumpkin puree and placing it in the fridge to keep it cool. This step is important because cold ingredients help create a flaky, tender scone by preventing the butter from melting too quickly when baking.
Grate or finely dice the frozen unsalted butter into pea-sized pieces. This step is essential for achieving a flaky texture, the chunks of cold butter will steam during baking and create little pockets of air in the dough. Place the butter in the freezer to keep it cold while you prepare the dry ingredients.
In a large bowl, whisk together the all-purpose flour, cornstarch, brown sugar, granulated sugar, cinnamon, pumpkin pie spice, baking powder, baking soda, and salt. Whisking helps distribute the ingredients evenly, ensuring a well-balanced dough.
Remove the frozen butter from the freezer and add it to the bowl of dry ingredients. Using a pastry cutter or fork, cut the butter into the flour mixture until the butter is broken down into pea-sized chunks. This step ensures the butter is evenly distributed throughout the dough, which is key to achieving the perfect scone texture.
Combine the pumpkin puree, sourdough starter, vanilla extract, and cold heavy cream. Stir until just combined. The key here is to handle the dough as little as possible to maintain its flaky, tender texture. The dough should come together easily but should not be over-mixed.
Lightly dust the plastic wrap and dough with flour to prevent it from sticking to your hands. Wrap the dough tightly in plastic wrap and refrigerate it for at least 30 minutes. If you’re planning ahead, you can let the dough chill overnight for up to 24 hours. This resting time allows the flavors to develop and the gluten to relax, resulting in a more flavorful and tender scone.
Once you’re ready to bake, preheat your oven to 400°F (200°C). Line your large baking sheet with parchment paper.
Turn the chilled dough out onto a clean surface and flatten it into a 1-inch thick circle. Using a bench scraper or a sharp knife, cut the dough into 8 equal pieces.
Place the unbaked scones on a prepared baking sheet, leaving about 2 inches of space between each one. Pop the baking sheet into the freezer for about 10 minutes to re-chill the butter and ensure the scones hold their shape during baking.
Once the oven is fully preheated, remove the scones from the freezer and immediately place the baking sheet on the middle oven rack. Bake for 15-20 minutes, or until the scones are golden brown on the edges.
While the scones are baking, prepare the glaze. In a small bowl, combine the melted butter, powdered sugar, strong brewed coffee, maple extract, and pumpkin pie spice. Stir until the glaze reaches a thick, pourable consistency. If it’s too thick, add a little milk, a teaspoon at a time.
Once the scones are done, transfer them to a wire rack to cool for about 10 minutes. You can drizzle the glaze over warm scones for a more melty effect, or wait until they’ve cooled for a thicker glaze that sets nicely on top.
To apply the glaze, use a spoon to drizzle it over the tops of the scones, or pour the glaze into a plastic bag and snip off a corner to pipe it on for a cleaner look.