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 to the flour mixture. Using a pastry blender or your fingertips, work the butter into the dry ingredients until the mixture resembles coarse crumbs with some pea-sized butter pieces remaining.
04 - In a separate bowl, whisk together whole milk, egg, and vanilla extract until combined.
05 - Pour the wet ingredients into the dry mixture. Gently fold with a spatula or wooden spoon just until the flour is mostly absorbed—do not overmix.
06 - Gently fold in the blueberries until evenly distributed throughout the dough.
07 - Turn the dough onto a lightly floured surface. Gently pat into a 1-inch thick rectangle, being careful not to overwork the dough.
08 - Using a 2.5-inch round biscuit cutter, cut out biscuits and place them on the prepared baking sheet. Gather scraps, gently pat together, and cut additional biscuits as needed.
09 - Sprinkle the tops of biscuits with coarse sugar if desired for extra crunch and sweetness.
10 - Bake for 18–20 minutes or until biscuits are golden brown on top and cooked through. Cool on the baking sheet for 5 minutes before serving.