Preheat oven to 425 degrees F (220 degrees C).
Line a baking sheet with a tin foil
Whisk flour, baking powder, salt, and baking soda together in a large bowl.
Cut butter into flour mixture with a pastry blender until the mixture resembles coarse crumbs, about 5 minutes.
Make a well in the center of butter and flour mixture. Pour in 3/4 cup buttermilk; stir until just combined.
Turn dough onto a floured work surface, pat together into a rectangle.
Fold the rectangle in thirds.
Turn dough a half turn, gather any crumbs, and flatten back into a rectangle. Repeat twice more, folding and pressing dough a total of three times.
Roll dough on a floured surface to about 1/2 inch thick.
Cut out 12 biscuits using a 2 1/2-inch round biscuit cutter or cup
Transfer biscuits to the prepared baking sheet. Press an indent into the top of each biscuit with your thumb.
Brush the tops of biscuits with 2 tablespoons buttermilk.
Bake in the preheated oven until browned, about 15 minutes.
