To prepare the stock: Heat the oil in a soup pot over medium heat. Add the onion and saute until lightly browned. Add the garlic and saute another minute or so. Add the tomato juice from the canned tomatoes, the cilantro stems and 3 ½ cups of the vegetable stock. Bring to a boil and reduce to a simmer at the back of the stove. Let it simmer away until you are ready to use it.

Preheat the broiler. Place the tomatoes, onions, garlic and serrano peppers on a large sheet pan. Drizzle with two tablespoons of the canola oil. Broil 4 to 5 inches from the heat source. When the onions, peppers, tomatoes and garlic begin to brown, turn them over to brown the other side, about 4 minutes. Remove individual vegetables as they finish cooking as some(especially the tomatoes) just take a little longer. Peel the garlic. Remove the seeds of the serrano pepper if you are not a fan of a lot of heat.

Puree the broiled vegetables in the blender with the chipotle, adding the reserved ½ cup of vegetable broth to thin it out a little.

Heat the remaining tablespoon of oil in a large pot over medium heat. Add the puree and cook, stirring, until it has thickened, about 5 to 10 minutes. Be careful of the boiling thickened puree – it really can jump out at you – stirring will reduce this. Add the strained stock, bring to a boil and then simmer, covered for 25 minutes. Add the salt.

Cut the small fresh corn tortilla into long thin (1/4 inch) strips and then in half (you will get about 20 strips), pan fry in canola until crisp. Remove from the oil and place on paper towel and lightly salt.

Just before serving, add the tortilla strips to the bottom of the serving bowl. Ladle in the soup. Add the avocado, cilantro and lime.