Optional: Prepare a 6 quart slow cooker with a plastic liner for easy cleanup.
Whisk the chicken broth, taco seasoning and tomato paste in the slow cooker. Lay the chicken breasts in the liquid and pour the remaining ingredients into the slow cooker. Stir everything together and cook on high for 5 hours or low for 7 hours. Remove the chicken breasts, shred them with a fork or a hand mixer and stir them back into the soup. Cook for another 30 minutes, until the chicken is completely done.
Serve hot with your favorite toppings like chipotle cheese tortilla strips, cheese, sour cream or cilantro.
Store refrigerated in an airtight container. Makes 8 heaping 1 cup servings.