Preheat oven to 425°. Toss strawberries with sugar; let stand, allowing juices from berries to release., For shortcake, whisk together flour, sugar, baking powder, baking soda and salt; cut in butter until mixture resembles coarse crumbs. In another bowl, whisk together egg and sour cream. Add to flour mixture; stir just until moistened. , On a lightly floured surface, gently knead dough 8-10 times. Transfer to a lightly greased baking sheet; roll or pat to a 7-1/2-in. circle. Bake until golden brown, 13-17 minutes. Remove to a wire rack; cool completely. , In a bowl, beat cream until it begins to thicken. Add sugar and vanilla; beat until stiff peaks form. , Using a long serrated knife, cut shortcake horizontally in half. Spoon half the strawberries (including juices) over top; spread with half the whipped cream. Add top of shortcake; layer with the remaining whipped cream and berries.