Add melted butter and brown sugar to a medium mixing bowl and mix.
Add eggs and whisk together.
Next, add peanut butter and vanilla extract, and mix to combine.
Pour in milk and stir until fully combined.
In a separate medium mixing bowl, stir oats, baking powder, and salt.
Pour wet ingredients into the bowl with the dry ingredients and mix until fully incorporated.
Finally, stir in the chocolate chips and raisins.
Spray a 7-inch pan with nonstick cooking spray. Pour the batter into the pan and spread out evenly. Then cover with foil.
Add a trivet to the inner pot, add 1 ½ cups of water. Place the pan on top of the trivet.
Lock the lid, and pressure cook on high for 60 minutes.
Once cook time is complete, quick-release the pressure.
Carefully, open the lid and remove the pan, uncover it, and let it cool for 10 minutes before serving.