If boiling your own chicken, add chicken stock to the stockpot over medium-high heat. Add a pinch of black pepper and place the chicken breasts in the stock. Boil until chicken reaches an internal temperature of 165F. Start checking internal temperature after around 10 minutes. After internal temperature has been reached, remove chicken and shred. Skim the chicken stock for any residue that you don't want to be in the base of your soup. Add chicken back into pot. Workaround: use rotisserie chicken.
To the shredded chicken and chicken stock, add all ingredients for the soup (omitting toppings + tortilla strips). Cook over medium heat, stirring occasionally, for 25-35 minutes.
For The Homemade Tortilla Strips
Preheat oven to 350F. Cut the yellow corn tortillas into strips (I use a pizza cutter). Toss with olive oil, kosher salt, black pepper, and tajin. Bake for 12-15 minutes or until lightly-browned.