• Preheat oven to 350°F. Line a baking sheet with a silicone baking mat or parchment paper.

Make the scone dough.

• In a large bowl, whisk together both flours, sugar, baking powder, cinnamon, and salt.
• Add the cold, cubed butter to the bowl with the flour mixture and cut in the butter using a pastry cutter (or two forks) until it is the texture of coarse meal.
• Add the blueberries and stir.
• In a small bowl, whisk together the buttermilk and 1 egg.
• Drizzle the buttermilk mixture over the flour mixture and gently toss/stir the mixtures together using a fork, just until a dough forms. Be careful not to over mix the dough.
• Place the dough onto a lightly floured surface and knead the dough twice. Use your hands to gently form the dough into a circle that's 1 inch thick. Use a pizza cutter, bench knife, or chef's knife dipped in flour to slice the dough circle into 6 triangles.
• Transfer the sliced dough to the prepared baking sheet, keeping the triangles arranged in a circular format but with about an inch of space between each.
• In a small bowl, lightly whisk the remaining egg with one Tablespoon of water to create an egg wash. Brush it over the top of each scone.

Make the streusel topping.

• In a medium bowl, whisk to combine the flour, brown sugar, cinnamon, and salt. Pour the melted butter over the dry ingredients and stir with a fork until a crumbly mixture forms. Sprinkle the streusel over the scones.

Bake the scones.

• Bake for 30 minutes or until the edges of each scone are golden brown. Transfer the scones to a wire rack to cool slightly before dusting with confectioners' sugar and serving.