Start by slicing the bananas into large slices, then transfer the bananas to a food processor or blender.
Blend them all together until a smooth uniform mixture is formed.
When that happens, stop blending and add the chocolate powder. Blend it all together again until fully combined.
Finally, add all the coconut oil and blend it all again until you get a unique mixture.
Get a small baking pan and pour all this mixture into it, and using a spatula, make it as flat as possible.
Now put it in the fridge and leave it there for at least 2 hours.
After the indicate time, unmold, slice and serve.