Step 1

Adjust oven rack to middle position and heat oven to 450 degrees. Grease 8-inch square baking pan with 1 tablespoon butter. Cut 10 tablespoons butter into ½-inch pieces and freeze until chilled, about 15 minutes. Let remaining 1 tablespoon butter sit at room temperature to soften.

Step 2

Whisk flour, baking powder, baking soda, and salt together in bowl. Add chilled butter to flour mixture and smash butter between your fingertips into pea-size pieces. Gently stir in buttermilk until no dry pockets of flour remain. Using rubber spatula, transfer dough to prepared pan.

Step 3

Lightly sprinkle extra flour evenly over dough to prevent sticking. Using your floured hands, pat dough into even layer and into corners of pan. Using bench scraper sprayed with vegetable oil spray, cut dough into 9 equal squares (2 cuts by 2 cuts), but do not separate. Bake until golden brown on top, about 30 minutes.

Step 4

Let biscuits cool in pan for 5 minutes. Using thin metal spatula, slide biscuits onto wire rack. Brush tops with softened butter. Let cool for 10 minutes. Pull biscuits apart at cuts and serve warm.