1Heat oven to 425°F. Grease bottom and sides of 9-inch square pan with shortening or cooking spray.
2Drain blueberries (from muffin mix); rinse and set aside. In medium bowl, stir together sour cream and egg; gradually stir in water and oil. Stir in muffin mix just until blended. Gently stir drained blueberries into batter. Spread batter in pan. Sprinkle with coarse sugar.
3Bake 20 to 25 minutes or until golden brown. Cool completely, about 1 hour. Meanwhile, in medium bowl, stir together strawberries, 1 cup fresh blueberries and 1/3 cup granulated sugar. Refrigerate until ready to serve.
4Cut shortcake into 9 squares; cut each square diagonally in half. Place 2 halves on each serving plate; top with berries and whipped topping.