Preheat the oven to 450°F.
In a large bowl, mix flour, baking powder, sugar, and salt. Cut the cold butter into the flour mixture. Make sure flour looks like coarse crumbles + butter chunks are flat.
Mix fresh blueberries into the flour mixture.
Add in the buttermilk and stir in gently till combined.
Fold-out dough onto a lightly floured surface. With flour-dusted hands, pat dough out into a rectangle. Fold the dough into thirds, stacking the dough into three layers. (Make sure you flour between each layer if the dough is wet).
Pat dough out until about 3/4 inch thick. Using a 2 1/2 - 3 inch circle cutter, gently cut out biscuits. DO NOT TWIST cutter, simply press down firmly.
Place the biscuit dough onto a cast iron pan. Place 1 - 2 inches apart.
Bake in the oven for 15-20 minutes, or until golden.