Dice the onion and jalapeño, mince the garlic, and drain and rinse the black beans and corn if using canned corn.
Heat a large pot over medium heat with a small drizzle of olive oil. Add the onion and jalapeño and cook for 4 to 5 minutes until softened.
Add the garlic and cook for 30 seconds. Stir in the taco seasoning and cook for another 30 seconds.
Place the chicken breast in the pot and pour in the chicken broth. Add the diced tomatoes, black beans, and corn and stir gently.
Bring the soup to a gentle boil, then reduce the heat to medium-low. Partially cover and simmer for 20 to 25 minutes until the chicken is fully cooked.
Remove the chicken and let it cool for a few minutes. Shred it with two forks into bite-sized pieces.
Return the shredded chicken to the pot and simmer for another 5 minutes so it absorbs the seasoned broth.
Taste and adjust the salt, pepper, taco seasoning, or heat as needed.
Adjust the consistency with extra chicken broth, or simmer uncovered for a few minutes if you want it thicker.
Prepare the toppings and serve the hot soup with shredded cheese, avocado, tortilla chips, lime, and optional cilantro.