Preheat your oven to 375°F. Line a baking sheet with parchment paper.
In a large bowl, whisk together flour, baking powder, and salt.
Grate frozen butter directly into the dry ingredients and toss gently with a fork to distribute evenly. This step ensures a perfect flaky texture.
In a separate bowl, mix heavy cream, sour cream, and vanilla extract. Add this mixture to the dry ingredients and gently stir until just combined.
Carefully fold in the blueberries and lemon zest, making sure not to overwork the dough.
Turn the dough onto a lightly floured surface and pat it into a ¾-inch thick disc. Cut into 8 wedges and place them on the baking sheet. Brush the tops with a little extra heavy cream for that golden finish.
Bake for 25-30 minutes, or until the scones are golden brown and crisp on the edges.
Make the Glaze: While the scones cool, whisk together the powdered sugar, melted butter, milk, lemon juice, and vanilla extract. Drizzle over warm scones for an extra touch of sweetness.