Add chicken breasts to the pot, bring back to a boil and cover with a lid, reducing heat to medium. Cook chicken for about 20 minutes or until chicken is no longer pink inside.
Using two forks, shred the cooled chicken. Transfer the shredded chicken to a bowl and add ½ a cup of the cooking liquid, 1 teaspoon chilli powder, 1 teaspoon cumin, green chiles, tomato paste, and a dash of salt and pepper.