Preheat the oven to <temperature>375<unit>°F</unit></temperature>

Add <quantity>6<unit>cups</unit></quantity> of all purpose flour and <quantity>1<unit>tsp</unit></quantity> of baking soda to a bowl

Add <quantity>5<unit>tsp</unit></quantity> of baking powder and <quantity>2<unit>tsp</unit></quantity> of salt. Whisk to sift and combine

Add <quantity>1½<unit>cups</unit></quantity> of cold butter into pieces. Place the bowl in the freezer for 20m until cold

Remove the bowl from the freezer and transfer half of the ingredients to a food processor. Pulse until combined, leaving some small butter chunks. Transfer to a large bowl and pulse the other half

Add <quantity>2¼<unit>cups</unit></quantity> cups of buttermilk and toss quickly to obtain a flaky dough

Dust a surface with flour and add a quarter of the dough at a time. Pat it down into a square, until it's about <quantity>2<unit>inches</unit></quantity> thick

Lightly dust the top with flour and roll out just a bit, to about <quantity>1<unit>inch</unit></quantity> thick

Cut the stack into 4 equal squares. Stack them on top of each other on a floured surface. Gently pat everything down

Roll it out to around <quantity>1.5<unit>inches</unit></quantity> thick, depending on how tall you would like the biscuits

Trim the rough edges of the dough

Cut the dough into 9 equal large square biscuits or 12 medium square biscuits

Brush the squares with heavy cream

Arrange the biscuits on a sheet tray lined with parchment paper at least <quantity>1<unit>inch</unit></quantity> apart

Sprinkle with flaky salt to taste

Bake for 15m in the middle rack, rotating once halfway through, until they are golden and fully expanded. The buttermilk biscuits are ready

Serve immediately or warm it up in the oven when serving later. Enjoy!