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.
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.
04 - In a small bowl, whisk together the heavy cream, egg, and vanilla extract. Pour over the flour-butter mixture.
05 - Gently fold until just combined. Add the blueberries and fold carefully to avoid crushing them.
06 - Turn the dough onto a lightly floured surface and pat into a 7-8 inch circle, about 1 inch thick.
07 - Cut into 8 wedges and place them on the prepared baking sheet, slightly apart.
08 - Brush the tops with extra cream and sprinkle with coarse sugar and a pinch of cinnamon, if desired.
09 - Bake for 18–22 minutes, until golden and firm.
10 - Cool for 10 minutes before serving.