Coat a 3-quart saucepan with a vegetable spray.
Add garlic, onion, and celery and sauté, stirring occasionally, until browned. Add cauliflower, bell pepper, carrots, and zucchini and cook, stirring to prevent burning, about 5 minutes.
Add chili powder and cumin and stir to combine. Add the beef broth, mushrooms, chilies, and tomatoes and cook, uncovered, for 20 minutes or until vegetables are tender and flavors are blended.
Slowly add the cornmeal or grits, salt, pepper, and pinto beans, if using. Simmer about 5 to 8 minutes. If you prefer a thinner broth, reduce the amount of cornmeal or grits, or omit completely. Depending on the kind of chili powder used, you may need to add 1 tbsp (or less) brown sugar.
Serve the chili in large soup bowls. It is good garnished with scallions, cheese, and tortilla strips.