Blueberry Cinnamon Streusel Buttermilk Scones

Steps

1. Heat the oven to 400°F (200°C) and line a large baking sheet with parchment.
2. Make the streusel first: in a small bowl, mix the oats, the brown sugar, 25 g of the flour and 2 g of the cinnamon. Rub in 25 g of the cold butter with your fingertips until clumpy, then chill it.
3. In a large bowl, whisk the remaining flour, the granulated sugar, the baking powder, the baking soda, the salt, the remaining cinnamon and the lemon zest.
4. Cut the remaining cold butter into the flour mixture with a pastry cutter or your fingers until the pieces are pea-sized.
5. In a measuring cup, whisk the buttermilk, the egg and the vanilla; set aside 15 g of this mixture for brushing.
6. Pour the rest of the buttermilk mixture into the flour mixture and stir with a fork until shaggy.
7. Add the frozen blueberries straight from the freezer and fold gently just until the dough holds together; a few dry streaks are fine.
8. Turn the dough onto a lightly floured counter, divide it in half, and pat each half into a 7-inch round about 1 inch thick. Cut each round into 6 wedges and set the 12 wedges on the baking sheet.
9. Brush the tops with the reserved buttermilk mixture and press the chilled streusel onto them.
10. Bake 20 to 24 minutes, until the tops are golden and a toothpick in the center of a scone comes out clean.
11. Cool on the sheet 5 minutes, then move to a rack for at least 15 minutes before serving.