Mix flour, baking powder, salt, and sugar together with a whisk then cut in chilled butter. Use a pastry cutter, a fork, your hands, or whatever works for you, cut in the butter until it is about pea-size.
Add buttermilk slowly to the flour mixture until you have just enough where the dough separates from the sides of the bowl. Stir until just combined and transfer dough onto a floured work surface.
Sprinkle the top of the dough with flour and using your hands or a rolling pin press/roll the dough to about 1/2-inch thickness.
Put blueberries over dough and knead by folding the dough over onto itself, push it down, fold it again, push it down, fold it a third time, and then flatten out to about 1-inch thick.
Cut into biscuits with a biscuit cutter or a glass. (2-inch or 2 1/2 biscuit cutter)
Place biscuits in the cast iron skillet making sure the biscuits are touching. If you are using a baking tray, make sure the biscuits are touching as well.
Bake at 475° F for a total of 10-12 minutes – but around 6-8 minutes take the biscuits out of the oven and brush each biscuit liberally with melted salted butter – this is very important! Brush the tops and any exposed sides. Place biscuits back in the oven.
When you see the tops turning a light brown (and the blueberries burst), take them out. The temperature in the middle of the biscuits will remain very hot once out of the oven and will continue the cooking process. If you leave them in past this point, they will burn easily.
Let the biscuits cool in the pan for about 10 minutes. Then drizzle, or pour, the glaze over the biscuits.
Serve right away!
Notes
• It is important for the butter to be very cold which is why you should put it in the freezer for at least 10 minutes.
• If you prefer a plain glaze that is not lemon, here is a recipe!
Plain Glaze: Just whisk ingredients together
1 cup powdered sugar
3 Tbsp. milk (or more if not thin enough)
1/2 tsp. vanilla
• Store any leftover biscuits in an airtight container.