The night before, slice the corn tortillas into long, thin strips and spread out onto a baking sheet to dry out overnight. The dried strips will fry up faster and absorb less oil.
The next day, in a heavy pot, preheat 4 cups of vegetable oil at medium heat for 5-6 minutes. Once oil is hot, test it by dropping in a tortilla strip. If it fries rapidly, it;s ready. Fry the strips in 3-4 batches so you dont over crowd the pot. Transfer fried strips to a baking sheet lined with paper towels. While the strips fry, remove the stems and seeds from the chile pasilla, Tear chiles in half. Set aside. Once you are done with the strips. Using tongs or a large slotted spoon fry the torn chile pieces for a few seconds per side. Transfer to a plate lined with paper towel. Set aside.
Preheat a large skillet or comal to medium heat for a few minutes. Add the tomatoes, onions, garlic and serrano. Drizzle lightly with 1 tsp. of oil. Cook for 20 to 25 minutes, turning as needed. Remove the garlic after 15 minutes and let cool.
Once tomato mixture is ready, remove from heat. Remove skins from garlic. Transfer all of the ingredients to the blender, including ½ of the fried chile pasilla and 2 cups of broth. Blend on high until smooth, strain into bowl with a wire mesh strainer. If using a power blender, no need to strain. Cut the remaining chile pasilla into small pieces, set aside.
Pour in two tablespoons of oil into soup pot. Preheat to medium for a few minutes. Once its hot, add the strained tomato/chile mixture in. Season with salt and pepper to taste. Reduce heat and continue cooking for 20 minutes, until it reduces and becomes thick.
When ready, pour in the 5 remaining cups of broth. Add the oregano, bay leaves and epazote. Stir well to combine. Cook at a steady simmer for 15 to 20 minutes. Taste for salt. To plate, add a big handful of tortilla strips to the bottom of bowls. Ladle soup base over halfway up to tortilla strips. Squeeze in fresh lime, garnish with queso panela, crema, avocado and chile pasilla pieces.