Heat oven to 425℉ (220℃).
Line a sheet pan with parchment paper. Set aside.
Whisk together sour cream and buttermilk.
Refrigerate until needed.
Sift flour, baking powder, baking soda, and salt into a large mixing bowl.
Grate butter into flour and toss gently to combine.
Stir in buttermilk mixture just until mixed. DO NOT OVERWORK!
Turn out onto floured surface. (It's ok if the dough is a little rough and ready. It will come together as you fold it.)
Roll into a rectangle that is about ½ inch thick.
Fold the top third of the dough down.
Fold the bottom third up over the top.
Repeat rolling and folding 3 more times (for a total of 4).
Roll into a 10 inch x 12 inch rectangle that is ¾ inch thick.
Use a 3½ biscuit (or cookie) cutter to cut out biscuits.
Gather and re-roll scraps, being careful not to overwork the dough, until all dough is used.
Place biscuits, sides touching, on prepared sheet pan.
Bake for 20-25 minutes, or until golden brown.