Add the chicken stock, crushed tomatoes, corn, tortilla strips, and chicken breasts. Stir a couple of times to mix the ingredients together.
Making sure the Ninja Foodi pressure cooking lid has the silicone seal properly in place and the VENT/SEAL knob is set to SEAL. Turn the power on, set the front panel to pressure cook on high for 7 minutes, and press START.
After the timer has expired, allow the Foodi to vent naturally (i.e. don't touch anything) for 10 minutes. Then carefully turn the VENT/SEAL knob to VENT. (Watch out for overhead cabinets.)
When the venting is complete, open the lid and remove the chicken breasts. Using two forks, shred the chicken, then return the chicken to the Foodi, stirring to distribute the shredded chicken throughout the soup.
Serve while hot. Garnish with sliced avocado, sour cream, cilantro, and/or crunchy tortilla strips as desired. Pour yourself a glass of white wine and enjoy!