Place a 12" cast iron skillet in the oven and pre-heat to 450ºF/232ºC.
In a large mixing bowl, add the cold butter to the dry ingredients and sand*.
Add the wet ingredients to the lot and mix until just combined.
Mix in the cheese and thyme until combined.
Turn the dough onto a floured work surface and pat it down into a rectangular shape until it's 1/2" thick. Fold the dough into three even parts (fold the left side to the middle and then the right side to cover the left).
Pat the dough down and repeat the fold.
Repeat step 7.
Using a large round cookie cutter (or a glass turned upside down), cut out the biscuits. Flatten the excess dough and repeat until all the biscuits are cut out. There's no need to fold once the dough is flat.
Remove the skillet from the oven and grease it with a pastry brush.
Carefully add the biscuits to the pan and return the skillet to the oven.
Bake for 15 minutes.