Preheat oven to 300 degrees F (150 degrees C).
In a large bowl, mash the Banana (4) using a fork or potato masher.
Add in the Peanut Butter (1/2 cup) and Unsweetened Cocoa Powder (1/4 cup) into the mashed bananas. Combine till well mixed.
Add in the Old Fashioned Rolled Oats (3 cup), Salt (1 pinch) and Granulated Sugar (2 tablespoon) into the wet ingredients. Mix until the ingredients are well incorporated.
Transfer the mixture into an 8x8-inch greased or lined square pan.
Bake it for 20-25 mins, or until a toothpick comes out clean.
Let it cool down before slicing and serving!