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 smooth.
05 - Pour wet ingredients into dry mixture and stir gently until barely combined. Do not overmix.
06 - Fold blueberries into dough gently just until distributed.
07 - Turn dough onto lightly floured surface. Pat gently into a 1-inch thick rectangle.
08 - Cut out rounds using a 2.5-inch biscuit cutter. Gather 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 to 20 minutes until tops are golden brown. Cool for 5 minutes before serving.