Whisk together dry ingredients: flour, sugar, baking powder, cinnamon, and salt in a large (preferably metal) bowl.
Grate frozen butter using a box grater and combine with the flour mixture using a pastry cutter (or two butter knives or a fork works also). Set aside in the fridge or freezer.
In a small bowl, whisk together ⅔ cup heavy cream, the egg, and vanilla.
Drizzle cream mixture over the flour mixture, add blueberries, then mix together with a spatula until everything is moist. Combine in this order. (Otherwise, the blueberries will clump up.)
Transfer mixture to a lightly floured countertop. If mixture appears too moist, sprinkle lightly with flour on top. If too dry, add a little more heavy cream. Work the dough, separating the dough into 2 equal parts.
Press each half of the dough into two 6-inch discs, about 1 inch thick. Cut each disc into 8 wedges with a sharp knife, pizza cutter or bench scraper.
Place wedges on a baking stone or cookie sheet lined with parchment paper about 2 inches apart.
Brush scones with 1-2 tbsp heavy cream and sprinkle with sugar (or coarse sugar if you have it) to give the top a crunch.
Free up a shelf in your refrigerator to chill the scones for at least 15 minutes.
In the meantime, preheat the oven to 400°F.
Bake scones for 22 minutes or until golden brown around the edges.
While scones are baking, whip up quick and easy icing by mixing ½ cup of powdered sugar with 1 tbsp milk in a small bowl.
Remove scones from the oven and cool briefly before topping with icing.