In a medium bowl, beat together butter and sugar. Add eggs one at a time and beat until uniform.
Add peanut butter, milk and vanilla and stir to combine.
In a large bowl, stir together oats, baking powder and salt. Add wet ingredients and mix until fully incorporated.
Fold in chocolate chips.
Coat the inside of a 7 inch baking pan or casserole with nonstick spray
Spread batter in pan and cover pan with foil.
Pour one cup of water in the Instant Pot and insert the steam rack. Carefully lower the pan or casserole on to the steam rack, then secure the lid, making sure the vent is closed.
Using the display panel select the MANUAL or PRESSURE COOK function*. Use the +/- keys and program the Instant Pot for 45 minutes.
When the time is up, let the pressure naturally release for 15 minutes, then quick-release the remaining pressure.
Carefully remove the pan and allow to cool for 10 minutes before serving.
Garnish with powdered sugar (optional). Keep covered and serve all week for a quick breakfast or snack.
Notes
The MANUAL and PRESSURE COOK buttons are interchangeable.