In the bottom of crockpot place chopped onion evenly. Place chicken breasts evenly over onion. Sprinkle salt, pepper, oregano, cumin and garlic evenly over chicken. Pour diced tomatoes, corn, enchilada sauce and chicken broth onto chicken. Mix to combine (without moving chicken).
Place lid on crockpot and cook for 4-5 hours on high or 6 hours on low until chicken is fork tender and can be easily shredded.
Remove chicken and shred. Replace in crockpot stirring into sauce. Place lid back on and let simmer on low until tortilla strips are done.
To bake tortilla strips, preheat oven to 375 degrees. Line a baking sheet. Cut 6-7 tortillas (either white tortillas or corn tortillas) into thin strips and place in an even row on baking sheet. Using a pastry brush, coat tortilla strips with olive oil or avocado oil. Sprinkle with a light coating of salt if desired. Bake for 20 minutes or until tortilla strips are crispy.
Turn off crockpot and ladle soup in a bowl. Top with optional toppings of sour cream, shredded cheese, cilantro, avocado, and baked tortilla strips. Enjoy.
