Preheat the oven to 425°F, and line a baking sheet with parchment paper. Set aside.
Place the flour, butter, sugar, baking powder, baking soda, and salt in a food processor. Pulse briefly to combine the ingredients until the flour resembles coarse cornmeal.
2 cups all-purpose flour, ¼ cup granulated sugar, 2 teaspoons baking powder, ½ teaspoon baking soda, ½ teaspoon salt, 8 tablespoons unsalted butter
Transfer the flour mixture to a large mixing bowl. Drizzle the buttermilk into the flour mixture, and stir until it just begins to come together. It shouldn’t be sticky or tacky.
½ to ¾ cup buttermilk
Turn the dough out onto a lightly floured surface and knead a couple of times. Form the dough into a rectangle shape about ½ - ¾ -inch thick.
Use a sharp knife or bench scraper to cut the dough into 6 equal squares. Transfer the dough to the prepared baking sheet spaced about 1-2 inches apart.
Use a pastry brush to lightly brush heavy cream over the tops of the dough. Then sprinkle with coarse sugar.
1 tablespoon heavy cream, 2 tablespoons coarse sugar
Bake for 14-16 minutes or until the tops are golden brown. Remove from the oven and allow to cool completely on a wire rack.