Tomato Tortilla Soup

Just made this for the first time last night and it was very good!
From Moosewood Restaurant's Simple Suppers

Serves 4-6 (Yield 9 cups)

Ingredients
3 cups diced onions
2 tsp olive oil
2 tsp ground cumin
1 tsp dried oregano
1 quart vegetable broth
1 28-ounce can of diced tomatoes
2 tsp minced canned chipotles in adobo sauce (or more--to your taste)
1 1/2 cups crumbled corn tortilla chips

Preparation
In a soup pot on medium heat, cook the onions in the oil for 5 minutes or until softened. Add the cumin and oregano and stir for a minute. Add the broth, tomatoes and chipotles, cover and bring to a boil. Reduce the heat and simmer for about 10 minutes.

Pulverize the tortilla chips in a blender. Add about 3 cups of the hot soup to the blender and puree until smooth. To make pouring easier, add another cup of hot soup and whirl on low speed. Stir the puree into the simmering soup pot. Serve hot.

(Garnish with chopped avocados, sour cream, grated cheese and/or chopped fresh cilantro)