In a large saucepan, cook onion and garlic in hot oil until onion is tender. Stir in mushrooms. Cook and stir 3 minutes more. Stir in undrained tomatoes, kidney beans, cumin, and chili powder.
Bring chili to boiling; reduce heat. Cover and simmer for 1 hour. If desired, top individual servings with sour cream. Makes 4 servings.