Chicken Tortilla Soup

2 tbs vegetable oil
1 cup yellow onion, chopped
2 tsp garlic, minced
4 cups chicken stock
10 oz tomato puree
1 small can tomato paste
1 tsp sugar
1/2 tsp salt
1 tsp Worcestershire
2 tsp chili powder
1/4 tsp pepper

4 tbs flour mixed with 1/2 cup water
1 lb cooked chicken, cubed
1 cup heavy cream
1/3 cup sour cream
10 oz processed cheese, cubed

1. Saute garlic and onions in oil in a large pot.
2. Add next 8 ingredients. Bring to a boil, reduce heat, and simmer 20 minutes.
3. Whisk flour/water mixture into soup. Bring to a boil, reduce heat, simmer 5 minutes.
4. Add chicken and simmer 5 minutes.
5. Add cream, sour cream, and cheese; stir until cheese is melted.

Serve with tortilla chips.