Start by preheating your oven to 450°F (232°C).

In a small bowl, mix ¾ cup of the blueberries with 2 tablespoons of granulated sugar and set them aside to macerate.

In a medium-sized mixing bowl, whisk together the flour, baking powder, and the remaining 1 tablespoon of granulated sugar until well combined.

Pour the buttermilk into the dry ingredients and gently stir until the dough just comes together—avoid overmixing to keep the texture light.

Gently fold in the sugared blueberries along with any juices that have collected in the bowl.

Pour the melted butter into the bottom of an 8×8-inch baking dish, making sure it coats the entire surface. Spoon the biscuit dough into the dish and spread it evenly to the edges.

Using a knife, lightly score the surface of the dough into 9 even squares (a 3×3 grid). Sprinkle the remaining ¼ cup of blueberries evenly over the top.

Bake in the preheated oven for 30 to 32 minutes, or until the tops are golden brown and the edges are crisp.

While the biscuits are baking, prepare the glaze by whisking together the confectioners’ sugar and milk in a medium bowl. Add more milk, a little at a time, until you reach your preferred glaze consistency.

Once the biscuits are baked, remove them from the oven and allow them to cool completely in the dish.

Drizzle the glaze generously over the cooled biscuits, then cut along the scored lines and serve.