Preheat the oven to 325 degrees F. Line a 24 count regular-size cupcake pan with cupcake liners. In a heavy-duty mixing bowl, cream together the butter and shortening on medium speed.
Add the eggs, 1 at a time, until completely combined. Scrape down the sides of the bowl with a rubber spatula.
Add the superfine sugar with the mixer set to low speed. Once combined, set the mixer to medium speed and mix for 5 minutes. Sift together the cake flour, cinnamon, salt, and baking powder. Begin to add the sifted dry ingredients to the batter, alternating with the warm milk. In a separate bowl, blend the plantain with a hand mixer.
Add the vanilla and the blended plantain to the batter. Fill the cupcake liners almost to the top.
Bake until the cake bounces back when you touch it, about 25 minutes.
Remove from the pan and place onto a tray to cool. Using a pastry bag and piping tip, frost the cupcakes with the Avocado Buttercream and top with 1 plantain chip.
In a heavy-duty mixing bowl, cream the butter until light and fluffy.
Add 3 cups powdered sugar. Scrape down the sides of the bowl with a rubber spatula. In a food processor, blend the avocados until smooth and add into the buttercream. Then add the remaining 4 cups powdered sugar.
Preheat the oven to 325 degrees F. Thinly slice the plantain, place on a baking sheet, and sprinkle with sugar.
Bake until the chips have browned completely, about 7 minutes.
