In a large pot over medium, stir onion, garlic, cumin, oregano, chilli powder, and pepper for 1 minute

Add broth, water, tomatoes (with juice), and green chillis. Cover and bring to boil

Meanwhile, stack tortillas and cut into half inch wide strips. Add to boiling broth.

Reduce heat, cover, and simmer for 15 mins, stirring occasionally

Cut chicken into small pieces and add to broth. Return to boil

Reduce heat, cover and simmer til chicken is cooked (about 5 mins)

Stir in cilantro.

Serve into bowls. Top with avocado and cheese