Add onions to a microwave-safe plate and cook for 1 minute, to soften. Coat Instant Pot with cooking spray. Add 1 teaspoon olive oil, ground beef, and softened onions. Brown beef and onions, stirring often to break up the beef into a crumble. If the meat sticks to the pot, add 2 tablespoons of water. Cook for 3 minutes. Add garlic and continue to cook until beef is completely browned about 2 additional minutes. Drain any fat from beef by pouring into a colander in the sink to drain. Once drained, add the meat back to pot.
To the cooked beef, mix in chopped tortillas, taco seasoning, and a little pepper. Sauté for 2 minutes. Stir most of the time.
Stir in chicken broth, tomatoes, corn, and green chilies. Cover instant pot and lock cover into place. Seal steam nozzle. Choose Soup setting. Set manually for 10 minutes. Once done, turn off instant pot. Let pressure release naturally for 5 minutes, then release any remaining pressure.
For each serving: Add 2 cups soup to each bowl. Add any optional toppings, if desired. I like mine topped with a little reduced-fat cheese.
This soup freezes great!