Roast the tomatoes in the oven at 400F for 20 minutes or so.
Saute 1.5 roughly chopped onions and 3 whole, peeled garlic cloves in a dollop of oil over medium heat. When the onion starts to turn brown (approx. 6-8 minutes) add the mixture to a blender or food processor along with the roasted tomatoes and a single chipotle. Combine well.
Saute the tomato-onion blender mixture in a dollop of oil over medium heat for a few minutes. Add 8 cups of broth along with 1/2 teaspoon of salt and some freshly cracked pepper.
Bring to a boil and add the chicken breast. Reduce heat to a simmer and let the chicken simmer in the broth until cooked all the way through and the center is no longer pink, approx. 15-20 minutes.
Remove the chicken and shred it using two forks. Add the chicken back to the broth and let it simmer for an additional 5 minutes or so. Take a taste for seasoning at this point. I added another 1/4 teaspoon of salt and some more freshly cracked pepper.
To make the tortilla strips, cut 3-4 corn tortillas into thin strips. Heat up a thin layer of oil over medium-high heat (I used approx. 1/4 cup canola oil). Once the oil is heated, add a handful of the tortilla strips and cook for 30-45 seconds or until they are just starting to turn golden brown. Cook the strips in 3 or 4 batches so that the oil remains at a constant temperature.
To serve, add shredded chicken to a bowl and top with the broth. Garnish with your choice of tortilla strips, Crema, chopped cilantro, or avocado bits.
Store leftovers in an airtight container in the fridge.