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 until well blended.
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 until combined.
05 - Pour wet ingredients into dry mixture. Gently mix until nearly combined.
06 - Add blueberries and fold in gently. Do not overmix to prevent tough biscuits.
07 - Turn dough onto floured surface. Gently pat into 1-inch thick rectangle.
08 - Cut out biscuits using 2.5-inch round cutter. Regroup scraps and repeat until all dough is used.
09 - Place biscuits on prepared baking sheet. Sprinkle tops with coarse sugar if using.
10 - Bake for 18–20 minutes until golden brown. Cool slightly before serving.