Combine strawberries with sugar and vanilla; mash slightly. Let stand at least 30 minutes, tossing occasionally., Preheat oven to 400°. For shortcakes, whisk together flour, 4 tablespoons sugar, baking powder, baking soda and salt. Cut in butter until crumbly. Add buttermilk; stir just until combined (do not overmix). Drop batter by 1/3 cupfuls 2 in. apart onto an ungreased baking sheet. Brush with 2 tablespoons heavy cream; sprinkle with remaining 1 tablespoon sugar. Bake until golden, 18-20 minutes. Remove to wire racks to cool completely., For topping, beat heavy whipping cream until it begins to thicken. Add sugar and vanilla; beat until soft peaks form. To serve, cut shortcakes in half; top with strawberries and whipped cream.