Mix the mashed bananas, brown sugar, eggs, butter, and milk then beat until fluffy.
Fold in the shifted self-rising flour and bicarbonate soda then add in the walnut and mix until well blended. Pour the mixture into the pressure cooker's inner pot.
Close the lid of the pressure cooker and turn it to the Lock position. OPEN OR REMOVE THE PRESSURE REGULATOR KNOB. On the Control Panel, press “Cake” (30 mins) menu button to start baking.
Once baking is completed, press the Keep Warm/Cancel button and switch off the power supply. Let it stand for 5 mins before opening the lid, serve and enjoy!