• Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
• In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
• Add the cold butter and cut it in using a pastry cutter, a fork, or your fingers until the mixture resembles coarse crumbs, and the butter is incorporated with the dry ingredients.
• In a small bowl, whisk together sour cream, egg, and vanilla. Pour into the dry ingredients and gently mix until mostly combined.
• Fold in the blueberries gently, being careful not to overmix (especially if using frozen blueberries).
• Turn the dough onto a floured surface. Cut the dough in half, place on piece on top of the other, gently pat it down. Cut the dough in half again, place one piece on top of the other, and pat it down. Do this until the dough comes together. The trick is to not over knead the dough, and this method of cutting the dough in half and placing on piece on top of the other is a great way to incorporate the flour into the wet ingredients without over mixing.
• Pat the dough into a 1-inch thick disk.
• Cut into 8 wedges and place on the prepared baking sheet, spaced 2 inches apart.
• Optional: Brush tops with cream or milk and sprinkle with coarse sugar.
• Bake for 18–22 minutes, until golden on top and a toothpick comes out clean.
• Let cool slightly before glazing.

Mascarpone Glaze

• In a medium bowl, mix the mascarpone, lemon juice, and powdered sugar. You can use a whisk or a hand mixer to do this.
• Add a bit more lemon juice or milk to thin the glaze out, or add more powdered sugar to make it thicker if it’s too runny.
• Drizzle over cooled scones and serve immediately!