01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together the flour, sugar, baking powder, salt, and Vietnamese cinnamon until well blended.
03 - Add the cold cubed butter and cut it into the dry ingredients using a pastry cutter or your fingers until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
04 - In a small bowl, whisk together the heavy cream, egg, and vanilla extract until combined.
05 - Pour the wet mixture over the flour-butter mixture. Gently fold with a spatula until just combined, being careful not to overwork the dough.
06 - Add the blueberries and fold carefully to distribute them evenly without crushing or breaking the berries.
07 - Turn the dough onto a lightly floured surface and gently pat it into a 7-8 inch circle, about 1 inch thick.
08 - Cut the circle into 8 equal wedges using a sharp knife. Place the wedges on the prepared baking sheet, leaving about 2 inches of space between each scone.
09 - Brush the tops of each scone with extra heavy cream. Sprinkle generously with coarse sugar and a pinch of Vietnamese cinnamon if desired.
10 - Bake for 18-22 minutes until the tops are golden brown and the scones feel firm when gently pressed in the center.
11 - Let the scones cool on the baking sheet for 10 minutes before transferring to a wire rack. Serve warm or at room temperature.