In stand mixer or hand mixer, mix together butter and sugar until well combined. Add in vanilla and eggs and mix.
In separate bowl combine the dry ingredients (flour salt and baking soda)
Smash together ripened bananas with milk.
With mixer on low, alternate adding the flour mixture and banana mixture until well combined. When combined, add in chopped walnuts.
Stir in chocolate chips with a spoon.
Pour batter into greased pan (that will fit inside the Instant Pot) and lightly cover with foil.
Place 1 cup of water in the bottom of the pot. Place foil covered pan on top of the trivet and lower into the pot.
Close and lock the lid and seal valve. Press manual or pressure cook and adjust time to 60 minutes. When timer goes off allow for a 10-12 minute. Open lid and carefully remove trivet with pan and remove foil