Preheat your oven to 400°F and line a baking tray with parchment paper. Keep all your ingredients chilled for maximum flakiness, especially the butter and buttermilk. This step is key for light, tender scones.
Sift flour, sugar, ground Earl Grey, baking powder, baking soda, and salt into a large bowl. Cut in cold butter with a pastry cutter until pea-sized crumbs form. Chill briefly while preparing the wet ingredients.
Whisk together egg and buttermilk in a small bowl. Rinse and gently pat dry the blackberries to avoid excess moisture, which can make the dough soggy.
Add wet ingredients to the dry mix and gently combine until just holding together. Fold in blackberries carefully to prevent crushing them. Flour may remain at the bottom; this is normal.
Turn dough onto a lightly floured surface and shape into a 1-inch thick disc. Cut into wedges or use a cookie cutter for rounds. Brush tops with a little buttermilk and sprinkle sugar for a golden finish.
Bake for 18–20 minutes until golden brown. Let scones cool slightly, then drizzle with lemon glaze made by whisking powdered sugar, lemon juice, vanilla, and zest