For the cupcakes:
Preheat the oven to 350°F. Line a standard muffin tin with paper cupcake liners.
In a medium bowl whisk together the flour, baking powder, baking soda, cinnamon, and salt.
In the bowl of a stand mixer beat the butter, granulated sugar, and brown sugar on medium-high speed until light and fluffy, about 3 minutes. Add the sour cream and vanilla and beat until combined. On medium speed add the eggs, one at a time, and beat until combined. Add the mashed bananas and beat until combined. On low speed gradually add the flour mixture and beat just until combined. Do not overmix.
Use a spring loaded scoop to fill each cupcake liner three-quarters full. Bake until golden brown and a toothpick inserted in the center comes out clean, 18 to 20 minutes. Remove to a wire rack and let cool completely.
Use a small knife or apple corer to cut a small hole in the middle of each cupcake. Place the dulce de leche in a zip top bag and snip one small corner. Squeeze out about 1 1/2 teaspoons of dulce de leche into each cupcake.
For the frosting:
In the bowl of an electric mixer beat the cream cheese and butter on medium-high until smooth and creamy. Sift the powdered sugar and cocoa powder into a large bowl. On low speed gradually add the sugar and cocoa, beating until incorporated. Increase the speed to high and blend until smooth and creamy.
Place the frosting into a piping bag fitted with a decorative tip. Pipe frosting onto the cupcakes, directly over the filling. Serve or store in an airtight container in the fridge for up to 3 days. Let come to room temperature before serving.