In a medium bowl, stir together flour, baking powder, and salt. While mixer is on low speed, alternate adding flour mixture and milk to the butter mixture until all ingredients are incorporated. Add in vanilla and mix until blended.
Spread batter into a greased 9 x 13 baking dish. Bake at 350 for 25 - 30 minutes or until golden on top. Remove from oven and cool completely.
Slice cooled shortcake into 12 squares. Split each square in half creating a top and bottom layer. Spread strawberries and whipped cream on each bottom layer of shortcake, and then top with the top layer of shortcake along with some more strawberries and whipped cream. Serve immediately.