Preheat oven to 375°.
To prepare the shortcakes, lightly spoon flour into dry measuring cups; level with a knife. Combine flour, sugar, unsweetened cocoa, baking soda, baking powder, and salt in a large bowl, stirring with a whisk. Cut in 1/4 cup butter with a pastry blender or 2 knives until mixture resembles coarse meal. Add buttermilk; stir just until moist. Knead lightly in bowl 5 to 6 times. Turn dough out onto a lightly floured surface; pat dough into an 8-inch circle on a baking sheet lined with parchment paper. Cut dough into 8 wedges, cutting into, but not through, dough. Bake at 375° for 18 minutes or until just firm to the touch. Remove from pan; cool on a wire rack. Place shortcake on a cutting board or work surface; cut along score lines with a serrated knife to form 8 wedges.
To prepare filling, combine 1/4 cup sugar and 2 tablespoons water in a small saucepan over medium-high heat; stir gently just until sugar dissolves. Cook, without stirring, until pale golden (about 4 minutes), gently swirling pan if needed to cook sugar evenly. Remove from heat; add cream and 1 teaspoon butter, stirring with a whisk until smooth. Cool 5 minutes.
Place whipped topping and 1/8 teaspoon cocoa in a medium bowl; fold just until combined. Split shortcakes in half horizontally using a serrated knife. Arrange about 1/4 cup bananas over bottom half of each shortcake; top each serving with about 1 teaspoon caramel sauce, about 2 tablespoons whipped topping mixture, and top of shortcake. Drizzle 1/2 teaspoon caramel sauce over top of each shortcake.
When mixing the dough for shortcakes, use a light hand and work quickly for the most tender cakes. If the recipe calls for kneading the dough, knead lightly only a few times so the dough doesn't become overworked.
Use a serrated knife to split the shortcakes. It will cut through the cakes without crumbling them.
You can bake the shortcakes up to a day ahead. Cool completely, and store at room temperature in a large zip-top plastic bag. To reheat, wrap in foil and heat at 350° for 10 minutes.
To freeze shortcakes, cool them completely, place in a heavy-duty zip-top plastic bag, and freeze up to two months. Thaw at room temperature, then reheat as instructed above.