Preheat your 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 granulated sugar.

Add the cold, cubed butter to the flour mixture. Use a pastry cutter or your fingers to blend until the mixture resembles coarse crumbs.

In a separate bowl, combine the buttermilk and vanilla extract. Pour this mixture into the flour mixture and stir until just combined.

Gently fold in the fresh blueberries, being careful not to overmix.

Turn the dough out onto a floured surface and knead gently for about 1 minute until it comes together.

Pat the dough into a rectangle about 1-inch thick. Cut out biscuits using a round cutter or a glass, and place them on the prepared baking sheet.

Bake for 12-15 minutes, or until the biscuits are golden brown on top.

While the biscuits are baking, prepare the glaze by whisking together the powdered sugar, milk, and vanilla extract in a small bowl until smooth.

Once the biscuits are done, remove them from the oven and let them cool slightly before drizzling the glaze over the top.