Add onions, bell peppers, celery, mushrooms, and garlic.
Cook until tender.
Set aside.
Brown ground beef and drain thoroughly.
Combine ground beef, vegetables, diced tomatoes, tomato paste, salt, cayenne, black pepper, fresh herbs, parmesan rind, and chili paste (if using) in a large stock pot.
Bring to a simmer, stirring occasionally.
Continue to cook, stirring occasionally, for about 2 hours.