Prep. Preheat the oven to 400°F (205°C) and line a baking sheet with parchment paper.
Mix dry ingredients. In a large bowl, whisk together the flour, sugar, baking powder, and salt.
Cut in the butter. Work the cold cubed butter into the flour with a pastry cutter or fingertips until the mixture looks like coarse crumbs with some pea-sized pieces remaining.
Add wet ingredients. Whisk the cream, egg, and vanilla in a small bowl; pour over the flour mixture and stir with a fork just until a shaggy dough forms. Do not overmix.
Fold in blueberries. Gently fold in the blueberries with as few strokes as possible.
Shape and cut. Pat the dough into an 8-inch circle about 3/4-inch thick on a lightly floured surface; cut into 8 wedges.
Bake. Arrange wedges 2 inches apart, brush with cream, and sprinkle with coarse sugar. Bake 18–22 minutes, until golden.
Glaze. Cool 10 minutes. Whisk the powdered sugar, cream, and vanilla until smooth and drizzle over the scones.