Add olive oil to the removable cooking pot.
Once the oil is hot, add the mushrooms and cook for 5-7 minutes allowing the mushroom to brown and cookout most of their liquid.
Stir the remaining ingredients into the pot except for the butter.
Secure and lock the lid and turn the pressure regulator knob to PRESSURE.
Set the time for 10 minutes and press start.
When the cooking time is complete, release the pressure using the natural release method.
Stir in the butter and fluff with a fork. For a vegan option, omit the butter and fluff with a fork. Serve immediately.