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 fingertips, work the butter into the flour 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 fully combined.
05 - Pour the wet ingredients into the dry mixture. Gently fold together with a spatula until almost fully incorporated—do not overmix.
06 - Gently fold in the blueberries just until distributed throughout the dough. Take care not to crush the berries.
07 - Turn the dough onto a lightly floured surface. Gently pat into a 1-inch thick rectangle, handling as little as possible.
08 - Using a 2.5-inch round cutter, cut out biscuits and place them on the prepared baking sheet. Gather scraps, gently press together, and cut additional biscuits as needed.
09 - Sprinkle the tops of each biscuit with coarse sugar if desired for extra texture and sweetness.
10 - Bake for 18 to 20 minutes or until biscuits are golden brown on top and cooked through. Cool on the baking sheet for 5 minutes before serving.