Spray the steel pot of your Instant Pot with a non-stick spray.
Add the following in this order - water, milk, steel cut oats, cinnamon powder.
Add mashed banana on top - do not stir anything.
Close the IP with its lid, make sure the valve is in sealing position.
Press the "porridge" button and set the time to 15 minutes. The pre-set time for porridge mode is 20 minutes so you have to use the "-" and "+" button to lower down the time to 15 minutes.
Once 15 minutes are up, you would hear a beep. Release the pressure immediately (aka do a quick release). Open the IP, and now give a good stir to the oatmeal.
Add brown sugar (or sweetener of choice) and mix till well combined.
Add a splash of vanilla extract and mix. Adding vanilla is optional, I love the flavor!
Transfer your warm banana oatmeal into serving bowls and top with sliced bananas, peanut butter, sliced almonds or any other topping of choice and enjoy!