Preheat oven to 375 degrees F. Place a medium-sized platter in the freezer.
Line 10 standard (2 3/4-inch wide) muffin cups with paper liners. Set aside.
To make the cupcakes, in a medium bowl and with an electric mixer, beat the peanut butter, sliced banana, oil and water together on medium speed until mostly smooth or only a few very small pieces of banana are visible. On low speed beat in the egg, cocoa powder and the cake mix. Increase speed to medium-high and beat for 1 minute or until batter is well blended.
Spoon an equal amount of batter into the lined muffin cups, filling each about 2/3 full. Bake on the center rack for 15 to 20 minutes or until a wooden pick inserted into the center of cakes comes out clean.
Remove cupcakes from the pan and place on the platter in the freezer. Freeze for 8 minutes to quickly cool the cupcakes.
While the cakes cool, make the frosting, with an electric mixer beat together the butter and peanut butter until smooth. Gradually beat in the powdered sugar and 1 1/2 teaspoons milk until frosting reaches a spreadable consistency. (If needed, add up to an extra 1/2 teaspoon of milk to make frosting smooth.) Frost cupcakes. Sprinkle the tops with an even amount of the chopped peanuts. Garnish the tops of each cake with a dried banana chip.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.