Add butter in an instant pot.
Turn on "Saute" mode.
When butter is melted, add onions, garlic, celery, carrots, mushrooms, Italian seasoning, poultry seasoning, salt, pepper and saute for a few minutes until veggies are partially softened and excess liquid from mushrooms has evaporated.
Add bread cubes, 1.5 cups broth and toss to combine. Add more broth if you prefer a "wet" stuffing. It should be slightly moist but not soggy and soaking wet.
Transfer this mixture to a greased round 1.5-2 quart baking dish.
Cover with aluminum foil and keep aside.
Place a trivet/rack with handles inside the pressure cooker.
Pour water.
Place the baking dish on top of the trivet.
Put the lid on and turn the the valve to “Sealing.”
Select “Manual” mode and set the timer for 15 minutes.
When cook time is over, allow pressure to release naturally for 10 minutes and then, turn valve to “Venting” and do a quick pressure release.
Remove baking dish from pressure cooker very carefully.
Allow it to sit for 5 minutes at room temperature.
Optional step: Remove aluminum foil and transfer baking dish to oven and broil for 5 minutes or until top is golden brown. Enjoy!