Preheat the oven to 180 degree Celsius. Line a loaf tin with paper and grease the sides.
In a grinder add the 4 over ripe bananas and jaggery. Puree the bananas and sugar together to a smooth liquid.
Take out the banana puree in a big mixing bowl. Add half cup of oil and vanilla essence. Mix it all together very well, using a spatula or a wooden spoon.
Now sieve, flour, baking powder, baking soda and salt directly on the banana mixture all in one go. Mix the wet and dry ingredients together using the cut and fold method.
This mixture is going to be a thick batter. But if you find it too thick you can add a few tablespoons of milk or water.
Now add the oats chocolate chips and walnuts and mix it again. Save some chocolate chips and walnuts for the top.
Pour the batter in the prepared tin, sprinkle chocolate and walnuts; and bake for 30 minutes or till the cake is cooked. (Test by putting a skewer in the center if it comes out clean the cake is cooked). 8. Cool on a wire rack. Cut into slices and serve.
