Add the three quarts of stock into the stock pot, slice the head of garlic across its center, do not peel, and add to the stock pot. Add the marjoram, thyme, and black pepper. Bring to a boil and reduce to a simmer for one hour while partially covered. It should be reduced to 7 cups, and remove and discard the garlic.
While the soup is simmering, dice the onion and tomato. Slice the jalapenos or serranos into thin strips. Boil the chicken breast, and use two forks to shred.
Place one cob of sweet corn (unshucked) into a microwave. Set a timer for four minutes and cook. Remove with a hot pad. Cut off the bottom of the cob about an inch above the base, and using a fork, pull the cob out of the husk, and it should slide out clean. Using a thin knife, like a filet knife, slice the kernels off the cob over a wide mixing bowl.
After simmering for an hour, add the salt, onions, chile, and corn to the stock, and simmer for an additional 7 minutes.
Add the cilantro, chicken, and tomatoes to the stock for three additional minutes.
Serve in individual bowls and top with diced avocados, pieces of pasilla peppers, and a wedge of lime.