Mexican Chicken Soup

(adapted from http://www.foodnetwork.com/recipes/ina-garten/mexican-chicken-soup-recipe/index.html )

3 cups of cooked, diced chicken

2 T olive oil
Salt and freshly ground black pepper
1 cup chopped onions (1 onion)
1/2 cup chopped celery (1 stalk)
1 cup chopped carrots (2 carrots)
2 large cloves garlic, chopped
1 quart (4 cups) chicken stock, preferably homemade
1 (14-ounce) can whole tomatoes in puree, crushed
1 or 2 jalapeno peppers, seeded and minced
1/2 teaspoon ground cumin
1/2 teaspoon ground coriander seed
1/4 cup chopped fresh cilantro leaves, optional

Heat 2 tablespoons of olive oil in a large pot or Dutch oven. Add the onion, celery, and carrots and cook over medium-low heat for 10 minutes, or until the onions start to brown. Add the garlic and cook for another 30 seconds. Add the chicken, chicken stock, tomatoes with their puree, jalapenos, cumin, coriander, salt, pepper and cilantro. Bring the soup to a boil, then lower the heat and simmer for 25 minutes. Top with sour cream or diced avocado, if desired.