Lightly spray a Dutch oven with vegetable oil. Add chicken, onion, and garlic. Cook over medium high heat until chicken is just tender, about 5 minutes. Stir in broth, chili peppers, cumin, and white pepper. Bring to a boil. Reduce heat and simmer 5 minutes, uncovered. Line each of 4 soup bowls with a tortilla. Spoon in chili and top with olives and cheese. Serve immediately.