Remove the stems and seeds from 2 dried pasilla chilies. Toast in a dry pan over medium-high heat for 10-20 seconds, without burning.
Measure 4 tablespoons of olive oil. Use half to soften ½ sliced large white onion and 4 minced garlic cloves over medium heat for 10 minutes.
Blend the onion, garlic, chilies and 625g of canned fire-roasted tomatoes with a stick blender until smooth. Heat the remaining olive oil in a pot and cook the purée for 5 minutes.
Add 680g of boneless skinless chicken breast, 8 cups of chicken broth, and 1½ teaspoons of kosher salt. Bring to a boil, cover and simmer gently for about 15 minutes, until the chicken reaches 165°F / 74°C.
Meanwhile, slice 6 corn tortillas into ¼in / 5mm strips. Heat ¼ cup of vegetable oil over medium-high heat. Fry in batches for 60-90 seconds, until crisp; drain on paper towels.
Remove and shred the chicken. Return it with 425g of canned black beans, drained, and ¾ cup of corn. Simmer for 3 minutes. Remove from the heat, add 2 tablespoons of lime juice and top with tortilla strips.
