Preheat oven to 425 degrees. Line a cookie sheet with parchment paper.
In a medium bowl, mix flour, baking powder, baking soda and salt together.
Using a food processor or a pastry cutter, cut butter into dry mixture until it resembles course meal.
Pour 3/4 cup buttermilk into butter-flour mix and stir just until combines. If too dry, add a little more buttermilk. It should hold together and be slightly sticky.
Turn out onto floured surface and fold over 3 or 4 times then pat into rectangle that is about 1/2" thick. Cut out 12 biscuits using a glass or biscuit cutter that is about 2-1/2" in diameter. You can take scraps and knead back together and make several more biscuits. These might not be as flaky but they will still be oh so good.
Place on prepared cookie sheet, wither 1" apart for crusty sides or almost touching for softer sides and higher biscuits.
Brush tops with the remaining 2 tablespoons buttermilk and place in oven for 15 minutes.
Remove from oven and serve immediately or let cool on wire rack then freeze for future use.
To make the best and flakiest biscuits make sure to use slightly frozen butter, ice cold buttermilk and handle as little as possible.