01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together flour, sugar, baking powder, and salt.
03 - Add cold, cubed butter. Cut in using a pastry blender or fingertips until mixture resembles coarse crumbs.
04 - In a separate bowl, whisk together milk, egg, and vanilla extract.
05 - Pour wet ingredients into the dry mixture and gently mix until nearly combined.
06 - Add blueberries and fold in gently—do not overmix.
07 - Turn dough onto a floured surface and gently pat into a 1-inch thick rectangle.
08 - Cut out biscuits with a 2.5-inch round cutter; regroup scraps and repeat cutting as needed.
09 - Place biscuits on prepared baking sheet. Sprinkle tops with coarse sugar if desired.
10 - Bake 18–20 minutes, or until golden brown. Cool slightly before serving.