In a mixing bowl, whisk together flour, baking powder, baking soda, sugar and salt for 30 seconds. Cover with plastic wrap and chill in freezer for 1 hour, place 1 stick of butter (8 Tbsp) in freezer to chill 1 hour as well. After 30 minutes of freezing, pour buttermilk into an airtight container and freeze 30 minutes (so they should all complete freezing at the same time).
Preheat oven to 425 degrees. Melt remaining 2 Tbsp butter in a microwave safe bowl, set aside. Remove butter from freezer and grate butter using the smaller holes of a box grater, then remove flour from freezer and toss grated butter into flour using a wooden spoon, until butter is evenly distributed. Remove buttermilk from freezer, stir and pour over flour mixture. Mix using a wooden spoon and one hand until mixture begins to come together adding 2 Tbsp milk (chilled from fridge) as needed toward end of mixing to help mixture come together.
Pat mixture over a floured surface to about 1-inch thick. Cut into circles using a biscuit cutter and transfer to a Silpat lined baking sheet. Spread tops generously with melted butter and bake in preheated oven 18 - 22 minutes until tops are nicely golden. Serve warm.