Prepare: Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper.

Mix Dry Ingredients: In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt.

Cut In Butter: Add the cold, cubed butter to the flour mixture. Using a pastry cutter, two forks, or your fingertips, work the butter into the flour until the mixture resembles coarse crumbs with a few pea-sized pieces of butter remaining.

Combine Wet Ingredients: In a small bowl or measuring jug, whisk together the cold heavy cream, cold egg, and vanilla extract.

Form Dough: Pour the wet ingredients into the flour-butter mixture. Gently stir with a fork until just combined and a shaggy dough begins to form. Carefully fold in the blueberries, trying not to break them.

Shape: Turn the dough out onto a lightly floured surface. Gently knead and pat the dough into a 7-inch circle, about 1-inch thick. Use a sharp knife or bench scraper to cut the circle into 8 equal wedges.

Chill: Place the scones on the prepared baking sheet, at least 2 inches apart. Brush the tops lightly with heavy cream and sprinkle generously with coarse sugar. Place the entire baking sheet in the freezer for 10-15 minutes to chill.

Bake: Bake for 18-22 minutes, or until the scones are golden brown on top and cooked through. Transfer to a wire rack to cool completely before glazing.

Glaze: While the scones cool, make the glaze. Whisk the sifted powdered sugar, 2 tablespoons of lemon juice, and lemon zest together in a small bowl. Add more lemon juice, one teaspoon at a time, until you reach a thick but pourable consistency. Drizzle over the cooled scones.