In a medium bowl stir together the flour, 2 teaspoons granulated sugar, baking powder, cream of tartar, and baking soda. Using a pastry cutter or two table knives, cut in the butter until mixture resembles coarse crumbs. Make a well in the center of flour mixture. Add buttermilk all at once to flour mixture. Using a fork, stir just until moistened.
Drop the dough into 2 mounds on a greased or parchment-lined baking sheet. If desired, sprinkle with coarse sugar. Bake, uncovered, in a 450 degrees oven for 10 to 12 minutes or until golden brown.
In a small bowl beat the whipping cream and 2 teaspoons granulated sugar with an electric mixer on medium speed or with a rotary beater until soft peaks form (tips curl).
Split the shortcakes into 2 layers. Place the bottom layers in 2 dessert bowls. Spoon some of the berries and whipped cream over bottom layers. Top with the remaining shortcake layers, berries, and whipped cream.