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 butter using a pastry blender or fingertips until mixture resembles coarse crumbs.
04 - In a separate bowl, whisk together milk, egg, and vanilla extract until fully incorporated.
05 - Pour wet ingredients into the dry mixture. Gently mix until nearly combined, being careful not to overmix.
06 - Gently fold blueberries into the dough until just distributed throughout.
07 - Turn dough onto a floured surface. Gently pat into a 1-inch thick rectangle. Cut out biscuits using a 2.5-inch round cutter. Regroup scraps and repeat cutting until all dough is used.
08 - Place biscuits on the prepared baking sheet. Sprinkle tops with coarse sugar if desired.
09 - Bake for 18–20 minutes, or until tops are golden brown. Cool slightly on the baking sheet before serving.