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 combined.
03 - Add cold, cubed butter to the flour mixture. 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 blended.
05 - Pour wet ingredients into the dry mixture. Gently mix until nearly combined, being careful not to overwork the dough.
06 - Add blueberries and fold in gently until just distributed throughout the dough.
07 - Turn dough onto a floured surface and gently pat into a 1-inch thick rectangle. Cut out biscuits using a 2.5-inch round cutter. Regroup scraps and repeat until all dough is used.
08 - Place biscuits on the prepared baking sheet. Sprinkle tops with coarse sugar if desired. Bake for 18 to 20 minutes until golden brown. Cool slightly before serving.