Select Sauté and add the oil to the inner pot. Once hot, add the onion, garlic, carrots, celery, and mushrooms, and cook for about 3 minutes, or until the vegetables start to soften.
Press Cancel and pour in the broth. Add the chicken, potatoes, rosemary, thyme, salt, pepper, and bay leaf. Stir to combine.
Lock the lid into place. Select Pressure Cook or Manual, and adjust the pressure to High and the time to 8 minutes. Make sure the steam release knob is in the sealed position. After cooking, naturally release the pressure for 10 minutes, then quick release any remaining pressure.
Unlock and remove the lid. Remove and discard the bay leaf.
Stir the stew and serve immediately, or place in an airtight container and refrigerate for up to 4 days.
You can substitute sweet potatoes for the white potatoes to make this recipe paleo-friendly.
You can use chicken thighs instead of chicken breasts for even more flavor.