Set the pressure cooker to "sear", press "start/stop", and add butter to melt. When melted, add celery, onions, carrots, and garlic, sauté for 4 minutes.
Pour in chicken stock and water then add mushrooms and tortellini.
Close and lock lid. Set the pressure cooker to "soup", adjust the time for 10 minutes, and press "start/stop".
When done, do a quick release and make sure all pressure is released before opening the lid.
Carefully open the lid and check the soup for seasoning. Add salt and pepper if needed. Ladle into serving bowls and garnish with cheese and serve.
