Start by grating your frozen butter into small pea-sized pieces using a cheese grater or a knife. This step is crucial for achieving the flaky texture that makes these scones so tender. Place the butter back in the freezer while you prepare the remaining ingredients. Keeping cold butter is key to successful scones.

In a large mixing bowl, combine the all-purpose flour, cornstarch, granulated sugar, baking powder, salt, and 1 tablespoon of lemon zest. These dry ingredients form the base of your scone dough. The addition of cornstarch helps create a tender crumb, which is key to the best scones.

Remove the frozen butter from the freezer and add it to the flour mixture. Use a pastry cutter or fork to cut the butter into the dry ingredients until the mixture resembles coarse crumbs with small pieces of butter throughout. The butter should remain cold to ensure the scones bake up flaky and tender.

In a separate bowl, mix the potato flake sourdough starter, heavy cream, vanilla extract, and fresh lemon juice. These wet ingredients will bring your dough together. Slowly pour this mixture into the flour mixture, gently stirring until just combined. Be careful not to overwork the dough, as this can lead to tough scones.

Just before the dough fully comes together, gently fold in the fresh blueberries. If you're using frozen blueberries, remember to rinse them until the water runs clear, pat them dry, and toss them in a tablespoon of flour before adding them to the dough. This helps prevent the berries from bleeding into the dough and ensures they stay evenly distributed.

Once the dough is mixed, form it into a dough ball, dust lightly with flour, and wrap it tightly in plastic wrap. Refrigerate the dough for at least 30 minutes to allow the butter to firm up and the flavors to come together. For an even better flavor and digestion benefits, you can refrigerate the dough overnight or up to 24 hours. This step is essential for creating tender scones with a flaky texture. This fermentation process is what makes the grains easier to digest.

Avoid using flour if possible since it has not gone through the fermentation process. However, a small amount of flour will be okay if it is needed.

Use a sharp knife or bench scraper to cut the dough into eight equal pieces. Using the bench scraper carefully lift each scone up off the work surface and place the unbaked scones onto a prepared baking sheet lined with parchment paper.

Be sure to leave about two inches of space between each one. Before baking, pop the baking sheet into the freezer for 10 minutes while the oven finishes preheating.

Bake the scones on the middle oven rack for 20-25 minutes, or until they are golden brown. The tops of the scones should have a nice, firm crust, and the interiors should be light and tender.

While the scones are baking, prepare the lemon glaze. In a small bowl, combine the melted butter, powdered sugar, lemon zest, and enough lemon juice to achieve a drizzling consistency. This lemon glaze adds a burst of fresh flavor that complements the juicy blueberries perfectly.

Once the scones are done baking, transfer them to a wire rack to cool slightly. Use a spoon to drizzle the lemon glaze over the top of the scones, spreading it with the back of the spoon to cover each scone evenly. Scones are best served fresh the same day, but are still delicious the next day.

If you have any scones left over, store them in an airtight container at room temperature for up to three days. For longer storage, wrap the scones tightly in plastic wrap and freeze them for up to three months. To reheat, simply pop them in a 350-degree oven for a few minutes until warmed through.