1. Preheat the oven to 400°F (200°C) and line a baking sheet with parchment paper.

2. In a large bowl, whisk together the flour, sugar, baking powder, and salt until well combined.

3. Add the cold butter cubes to the dry ingredients and use a pastry cutter or two forks to cut the butter in until the mixture resembles coarse crumbs.

4. Sprinkle the lemon zest over the flour mixture and toss gently to distribute.

5. In a separate bowl, whisk together the sourdough discard, heavy cream, egg, and vanilla extract until smooth.

6. Pour the wet ingredients into the dry mixture and fold gently with a spatula until just combined and no dry streaks remain.

7. Fold in the blueberries very gently to avoid crushing them.

8. Transfer the dough to a lightly floured surface and pat into a 1-inch thick circle or rectangle.

9. Use a sharp knife or cutter to divide the dough into 8 wedges or bite-sized pieces and place them on the prepared baking sheet.

10. Chill the shaped scones in the refrigerator for 10–15 minutes to firm up the butter.

11. Brush the tops with a little heavy cream or egg wash and sprinkle with coarse sugar if desired.

12. Bake for 18–22 minutes, or until the scones are golden brown and springy to the touch.

13. Allow the scones to cool on a wire rack for about 10 minutes before serving warm.