Tortilla Soup

1 T veg oil
1 onion
2 garlic cloves
1 T chili powder
2 T cumin
1/2 t oregano
1 bay leaf
6 c chicken stock
8oz tomato sauce
3/4 t salt
1 t sugar
1/4 t pepper
3 chicken breasts
sour cream
avocado
cheese
cilantro