Add the flour, baking powder and salt to a large bowl or food processor. Whisk to combine or pulse processor lightly.
Add the butter to the dry ingredients and combine until crumbs form. If using a bowl, use a pastry cutter, if using the food processor, pulse several times.
If using processor, transfer the mixture to a large bowl.
Form a well in the center of the mixture and pour in the buttermilk.
Fold together until the dough begins to come together.
Flour a smooth work surface and transfer the dough from the bowl.
Generously flour your hands and begin working the dough together.
Form or roll into ¾ inch thick rectangle.
Fold one long side into the center, then fold the other long side in **see notes
Rotate the dough so that it is horizontal to you.
Gently flatten the dough into a rectangle and fold the sides into the middle again.
Turn the dough again and fold the sides into the middle again.
Turn horizontally again and flatten dough into a rectangle about 1 ¼ inches thick.
Preheat the oven to 425 degrees F.
Generously butter a cast iron skillet or line a baking sheet with parchment paper or a silicone mat.
Use a 2 ½ or 3 inch biscuit cutter to cut the dough. Cut straight down and pull straight up, do not twist the cutter **see notes
Place the biscuits in the prepared cast iron skillet or on the baking sheet.
Brush the tops of the biscuits with a little extra milk, if you like.
Bake for 15-20 minutes or until golden brown.
Remove from the oven and brush with the melted butter, if desired.
Serve warm or at room temperature.
Store in an airtight container in the refrigerator for up to 5 days.