Preheat your oven to 400 F/ 204 C. Line a baking sheet with parchment paper; set aside.

In the bowl of a food processor: add the flour, baking powder, salt and sugar. Pulse just a few times to combine.

Add the butter. In short bursts, pulse 3-5 times. The mixture should look sandy and crumbly, with some large chunks of butter throughout.

In a large bowl: whisk the egg, sourdough starter, vanilla extract, heavy cream and citrus zest together.

Add the dry ingredients to the bowl with the wet ingredients. Mix gently with a rubber spatula to combine.

Fold in the fresh blueberries. If the mixture seems dry, add a drizzle of heavy cream. The dough should easily stick when pinched together with your fingertips. Bring the dough together in a large mound.

Using a ½ cup measure, portion the dough onto your lined baking sheet, keeping them rounded for added height when baked.

Sprinkle the tops with coarse sparkling sugar.

Bake on the center rack for 20-24+ minutes or until golden and set in the center when poked.

Cool on the pan for 1-2 minutes; then transfer to a wire rack to finish cooling completely.

Serve slightly warm or at room temperature for best texture.

Scones are best enjoyed fresh, on the same day that they are baked. Once completely cool, transfer to a plate and cover with foil or wrap; the texture will start to become more moist as they sit. Gently reheat in a low oven, if you prefer.

Wrap cooled, baked scones in plastic wrap and then a layer of foil. Freeze up to 1-3 months. Uncover and thaw at room temperature. Bake @ 300 F/ 150 C on a parchment-lined tray for 10-15 minutes.

After you have portioned the dough into balls, place onto a parchment-lined plate. Freeze until solid. Transfer to an airtight container or zip-top bag. Freeze for 1-3 months. To bake, place the frozen dough onto a parchment-lined baking sheet; bake for 28-30 minutes.