Whisk the flour, sugar, baking powder, cinnamon and salt together in a large bowl. Grate the frozen butter using a box grater. Add it to the flour mixture and combine with a pastry cutter, two forks, or your fingers until the mixture comes together in pea-sized crumbs. Place in the refrigerator or freezer as you mix the wet ingredients together.
Whisk 1/2 cup heavy cream, the egg and vanilla extract together in a small bowl. Drizzle over the flour mixture, add the blueberries, then mix together until everything appears moistened.
Pour onto the counter and, with floured hands, work the dough into a ball as best you can. Dough will be sticky. If it’s too sticky, add a little more flour. If it seems too dry, add 1-2 more tablespoons heavy cream. Press into an 8-inch disc and, with a sharp knife or bench scraper, cut into 8 wedges.
Brush scones with remaining heavy cream and for extra crunch, sprinkle with coarse sugar. (You can do this before or after refrigerating in the next step.)
Place scones on a plate or lined baking sheet (if your fridge has space) and refrigerate for at least 15 minutes.
Meanwhile, preheat oven to 204°C.
Line a large baking sheet with parchment paper or silicone baking mat. After refrigerating, arrange scones 2-3 inches apart on the prepared baking sheet(s).
Bake for 22-25 minutes or until golden brown around the edges and lightly browned on top. Remove from the oven and cool for a few minutes before topping with vanilla icing.
Leftover iced or un-iced scones keep well at room temperature for 2 days or in the refrigerator for 5 days.
