Sift the flour, cocoa and baking powder into a bowl. Add the granulated sugar and combine everything with a wooden spoon.
Add milk, oil and eggs. Mix until well combined.
Pour the batter into an 8-inch (20cm) round cake pan lined with a sheet of baking parchment. Bake in a preheated oven at 360°F/180°C for 20 minutes or until an inserted skewer comes out clean. Take out and let it cool completely.
Peanut butter frosting:
In a food processor combine all the ingredients and pulse until well combined. It will only take a few seconds.
Assembling the cake:
With a knife, make a cut around the top of the cake in a circle (about 0.5 inch/1.5 cm from the edge). Don’t push the knife down completely. The circle will act as a boundary. Now get a spoon and hollow out the center of the cake (up to the boundary). Keep the cake crumbs for later.
Fill the hollowed out area with ½ of the frosting and spread it around evenly. Top this with sliced bananas up to the top. Now spread the rest of the filling across the cake and cover this with the cake crumbs.
Optional: cover the sides with thick chocolate syrup (see note 3).
Place this in the fridge for 2-3 hours before slicing.
Note
This recipe was made in an 8-inch/20cm wide round cake pan.
The number of servings is individual but it can be somewhere between 8-10 slices.
Chocolate syrup is completely optional and can be omitted. Alternatively the frosting can be used to coat the sides as well.
Powdered sugar (US) = Icing sugar (UK).
The cake base can be baked ahead, if needed. The frosting cannot be made ahead. However, you can make the whole cake ahead but in this case I highly recommend storing it in an air-tight cake container in the fridge to prevent the crumbs from going dry.
Chilling is not included in the preparation time. Count with 2-3 hours.
