01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together flour, sugar, baking powder, and salt until well blended.
03 - Add cold cubed butter to the flour mixture. Using a pastry cutter or fingertips, work butter into dry ingredients until mixture resembles coarse crumbs.
04 - In a small bowl, whisk together milk, egg, and vanilla extract until combined.
05 - Pour wet ingredients into flour mixture. Stir gently until just combined—do not overmix.
06 - Gently fold blueberries into the dough until evenly distributed.
07 - Turn dough onto a lightly floured surface. Pat into a 1-inch thick round. Cut out biscuits using a 2.5-inch round cutter, re-rolling scraps as needed.
08 - Place biscuits on prepared baking sheet, spacing them 1 inch apart.
09 - Bake for 18-20 minutes until golden brown and cooked through.
10 - While biscuits cool slightly, whisk together powdered sugar, 2-3 teaspoons milk, and vanilla extract until smooth.
11 - Drizzle glaze over warm biscuits before serving.