1. Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
2. In a large bowl, whisk together flour, sugar, baking powder, and salt.
3. Grate frozen butter into the dry ingredients and use a pastry cutter or your hands to mix until a crumbly texture forms.
4. In a separate bowl, whisk together heavy cream (or buttermilk), egg, and vanilla extract.
5. Gently fold the wet ingredients into the dry mixture until just combined.
6. Carefully fold in fresh or frozen blueberries, being cautious not to overmix.
7. Turn the dough onto a floured surface and shape it into a disk about 1-inch thick.
8. Cut the disk into equal wedges and place them on the prepared baking sheet.
9. Brush the tops of the scones with heavy cream and sprinkle with coarse sugar for added crunch.
10. Bake for 20-25 minutes until the scones are golden brown.
11. Let the scones cool on the baking sheet for a few minutes, then transfer them to a wire rack.
12. If desired, prepare a glaze by mixing powdered sugar with lemon juice or milk and drizzle over the cooled scones.
13. Serve fresh and enjoy for breakfast or teatime.
14. Store leftover scones at room temperature for up to 2-3 days.
15. Freeze unbaked scone dough for later use if needed.