Combine sliced strawberries and 1/4 cup sugar. Cover strawberry mixture, and set aside.
Combine all-purpose flour, baking powder, and 1/4 cup sugar; cut in butter with a pastry blender or fork until mixture is crumbly.
Whisk together eggs, sour cream, and vanilla until blended; add to flour mixture, stirring just until dry ingredients are moistened.
Turn dough out onto a lightly floured surface, and knead 6 times. Pat dough into an 8-inch square; cut into 16 (2-inch) squares. Place dough on a lightly greased baking sheet.
Bake at 425° for 9 to 11 minutes or until golden.
Beat whipping cream at medium speed with an electric mixer until foamy, and gradually add 2 tablespoons sugar, beating mixture at high speed until stiff peaks form.
Remove shortcakes from oven, and split in half horizontally. Combine strawberry jam and chopped mint; spread cut sides of bottom shortcake halves evenly with jam mixture, and top evenly with half of strawberry mixture. Cover mixture evenly with whipped cream; top with remaining strawberry mixture and remaining shortcake halves. Garnish, if desired. Serve immediately.
Round Shortcakes: Pat dough toa 1/2-inch thickness, and cut with a 3-inch round cutter. Place dough on a lightly greased baking sheet, and proceed with recipe as directed. Makes 12 servings.
Shortcake Shortcut: Combine 1 (16-ounce) container strawberries, sliced, and 1/4 cup sugar; cover and set aside. Brush 9 large frozen biscuits with 3 tablespoons melted butter. Combine 3 tablespoons sugar and 1 teaspoon ground cinnamon; sprinkle over biscuits. Bake according to package directions. Serve immediately, with strawberry mixture and whipped cream, to 8 happy friends.