Sauté the vegetables: Remove the lid from a 3-quart Instant Pot and select SAUTÉ. Add the oil, then add the onion, carrot, celery, and garlic. Season with salt, pepper, and Italian seasoning. Cook, stirring occasionally, until the vegetables begin to soften, about 4 to 5 minutes.
Pressure cook the soup: Press CANCEL. Add the chicken, green beans, and chicken broth. Secure the lid and set the valve to SEALING. Select PRESSURE COOK on HIGH and set the timer for 15 minutes.
Release the pressure: When cooking is complete, allow the pressure to release naturally for about 10 minutes, or carefully perform a quick release according to the manufacturer’s instructions. Once the pin drops, unlock and remove the lid.
Cook the noodles: Select SAUTÉ. Bring the soup to a gentle boil, add the noodles, and cook until al dente, about 4 to 5 minutes.
Shred the chicken: While the noodles cook, shred the chicken into bite-size pieces using two forks.
Finish and serve: Press CANCEL. Taste and adjust seasoning if needed. Ladle the soup into a bowl and serve warm.
Notes
Use Caution With Quick Release: When releasing pressure, turn the valve carefully and keep your hands and face away from the steam. Soups contain a lot of liquid, so steam release can be strong.
Natural Release for Extra Safety: For a gentler option, let the pressure release naturally before opening the lid. This works well and does not affect the texture or flavor of the soup.
Add Noodles After Pressure Cooking: Always cook the noodles after pressure cooking to prevent them from becoming overly soft or breaking apart.