To make chicken stock: Place all ingredients in a stockpot along with 8 quarts of water. You can use the bones from Cristina's Roasted Chicken recipe. Simmer until all vegetables are soft (approximately 45 minutes). Strain the vegetables. Cool and refrigerate overnight.
To make the soup: Heat corn oil in a stockpot and sauté 3 corn tortillas, cut into 1/2-inch strips.
In a food processor, chop the garlic, onions and seeded jalapeño.
Add the onion, garlic and jalapeño mixture to the pot and sauté for 10 minutes. Add the can of chopped tomatoes along with 2 quarts of chicken stock. Bring to a boil.
Reduce heat, cover and simmer for 15 minutes. Add ground cumin and simmer for 10 more minutes. Season with salt and pepper.
Transfer soup to a blender and puree until smooth. Strain into a clean pot. Garnish with chopped avocado and shredded cheese.