- Preheat oven to 425 degrees F (220 degrees C).
- Line a baking sheet with a silicone baking mat or parchment paper.
- 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 the 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.
- 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.