In a small bowl, mix together the stock, vinegar, agave nectar, cayenne pepper, oregano, thyme, basil, and salt.
Heat the 1 oil in large pan over medium heat. Add the onion, celery, garlic and cook for about 8 minutes, or until soft and fragrant.
Add the collard greens, and vinegar-agave nectar mixture and cover the pan. Cook for about 10 minutes, or until greens are tender.
Stir in the beans and tomatoes and cooked until heated throughout, another 2 or 3 minutes. Season with salt and pepper to taste.
Serve over brown rice and top with hot sauce, if using.