1. Heat oven to 350 degrees F. Lightly coat 18 standard-size muffin-pan cups with nonstick cooking spray.
2. Whisk together flour, sugar, cocoa powder, baking soda and salt in small bowl.
3. Stir together prune butter, oil, eggs, dissolved espresso and vanilla in large bowl. Stir in flour mixture until blended. Spoon batter evenly into prepared muffin cups, filling each cup about halfway full.
4. Bake in 350 degree F oven 17 to 20 minutes or until tops spring back when lightly touched. Cool cupcakes in pan for 3 minutes. Turn out onto wire rack to cool completely.
5. Just before serving, frost each cupcake with a tablespoonful of whipped topping. Dust with cocoa powder through fine-mesh sieve.