Spray the bottom of a 7" spring form pan or a 6 cup Bundt pan with cooking spray. Set aside.
In a medium mixing bowl, combine flour (use a spoon to add flour to measuring cups and then level), baking powder, baking soda, cinnamon and salt. Make a well in the center and set aside.
In another bowl, combine the egg, mashed bananas, sugar and oil. Add the wet mixture all at once to the well in the middle of the dry mixture.
Stir just until moistened (batter should be lumpy) and fold in nuts and chocolate chips if desired.
Spoon batter into prepared pan. Top with additional nuts and chips if desired. Lightly cover the pan with a paper towel and then cover with foil.
Pour 1 1/2 cups water into the Crockpot Express inner pot. Place trivet in the pot. Using an aluminum foil sling or trivet with handles, lower the spring form pan into the Crockpot Express and set onto the trivet.
Make sure the steam release valve is closed. Press Multigrain (defaults to 40) and then Start. (if you're using a Bundt pan, reduce the time to 35 minutes.) Once pressure has released naturally for 5 minutes, release any remaining pressure and remove from the pot. Remove the aluminum foil cover and allow to cool in the pan on a baking rack.