In a bowl, peel and add the over ripe bananas.
Using a fork, mash it completely.
Sift and add the cocoa powder (to avoid lumps) and powdered jaggery.
Whisk well until the jaggery dissolves completely.
Now add milk (should be at room temperature)
Add the vanilla essence and oil. Whisk this and keep aside.
In another bowl, sift the banana flour twice, add the baking powder and baking soda along with a pinch of salt.
Now carefully pour the wet ingredients into the dry ingredients and gently mix everything using a spatula.
Pour the cake batter into a square tin lined with parchment paper. Sprinkle the dark chocolate chips on top and bake at 180 Degree Celsius for 40 minutes.
Once baked, lift and remove the parchment paper carefully from the baking tin, allow it to cool on a rack and then slice them into desired pieces.