Place tomatoes in boiling water for about 2 minutes.
Remove tomatoes and in a food processor, blend them with the onion and garlic.
Heat 2 tablespoons of the vegetable oil in a 2 Litre sauce pan. Add the blended tomato mixture. Cook until it changes colour and has a pleasant cooked taste.
Add the broth and heat until it just starts to boil. Simmer and add the Epazote leaves, salt and pepper.
In a separate pan or griddle roast the dried pasilla chilies in the remaining vegetable oil until they change colour but do not blacken. If burnt, the chillies will taste bitter and unpleasant.
To serve, use deep bowls. Pour or ladle in the very hot broth mixture. Place a handful of chips in the soup and garnish with grated cheese, avocado, and sour cream. Serve immediately so the chips do not get soggy.
Serve the grilled chillies on the side for individuals to use to their taste.