Preheat the oven to 425°F (220°C) and line a baking sheet with parchment paper.
In a large mixing bowl, whisk together the flour, baking powder, salt, and sugar until combined.
Add the cold, cubed butter to the flour mixture. Use a pastry cutter or fork to cut in the butter until the mixture resembles coarse crumbs.
In another bowl, mix together the buttermilk and vanilla extract. Pour this mixture into the flour mixture and stir gently until just combined.
Fold in the fresh blueberries carefully to avoid smashing them.
Turn the dough out onto a floured surface and knead gently for about 1 minute. Pat the dough into a rectangle about 1-inch thick.
Cut the biscuits using a knife or biscuit cutter and place them on the prepared baking sheet, spacing them about an inch apart.
If desired, sprinkle a little sugar on top of each biscuit for added sweetness.
Bake in the preheated oven for 12-15 minutes, or until the biscuits are golden brown.
Remove from the oven and let cool on a cooling rack for a few minutes before serving.