Preheat a standard cast iron skillet on the stove or in the oven at 425F

MAKE THE BISCUIT DOUGH

Add the flour, salt, sugar, and baking powder to a mixing bowl or bowl of a food processor and mix to combine.  

Grate/cut the cold butter into the dry ingredients.  

Add the egg and milk - then stir until the wet ingredients are combined with the butter and flour mixture in a shaggy dough.

SHAPE AND CUT THE BISCUITS

Turn the biscuits out onto a lightly floured surface and fold the dough over onto itself until the dough sticks together in one piece.  Then, flatten the biscuit dough with your hand or a rolling pin into a thick rectangle and tri-fold the dough.  Then flatten it out and tri-fold it again.  

Repeat this flattening and folding process 5-6 times.  Never knead the dough, just flatten and fold it -this technique is what will give you flaky biscuits with lots of layers. 

Flatten or roll the biscuit dough out into a thick rectangle and use a biscuit cutter or bench scraper to cut the biscuits.

BAKE THE BISCUITS

Add 2 tablespoons of butter to the hot skillet (don't skip this step!  This bit of butter is the key ingredient for brown butter bottoms on your biscuits) and return it to the preheated oven for a few minutes until the butter is a medium-brown color.  

Once the butter is browned, make sure to spread it around to cover the entire surface of the skillet, then add the cut biscuits and bake at 425 for 15-18 minutes until the tops just start to turn golden brown.  Serve immediately or store for later.