Place all ingredients into pot in the following order: chicken, potatoes, carrots, celery, onions, tomatoes, rosemary, salt, pepper, and garlic powder. Then pour chicken broth over the top of everything.
Close lid and steam valve and set to high pressure for 10 minutes, then allow steam to naturally release.
When done lift lid. Use forks to shred chicken. Set pot to saute.
In a bowl whisk together your 1/2 c of water or use heavy whipping cream to make creamier. Add your cornstarch to the liquid and whisk until smooth.
When soup is boiling in pot add this mixture and stir. Allow to bubble for 3-4 minutes so liquid thickens, then serve.