Turn the Instant Pot to sauté. Once heated add the butter, onions, celery and carrots. Cook for 2 minutes, stirring occasionally. Add the garlic and cook for 1 more minute. Turn the Instant Pot off.
Add the chicken to the Instant Pot, then the chicken broth, oregano, bay leaf, salt and pepper.
Place the lid on the Instant Pot and lock it. Make sure the lever is set to seal. Press the manual button and set the time for 8 minutes.
When the time is up let the pressure manually release for 5 minutes, then release the pressure and remove the lid.
Remove the chicken from the Instant Pot and shred it. Also remove the bay leaf.
Turn the Instant Pot to sauté and add the noodles. Cook according to the directions on the box.
Turn Instant Pot off and add the chicken back in. Stir in the Parmesan cheese then serve.