Heat frying pan, add oil, saute onion for 3-4 minutes on medium heat. Add minced garlic, cook for 30 seconds to 1 minute.
Remove onion and garlic from the frying pan, add beef to the pan, cook on medium-high for 7-10 minutes. Drain some excess fat if there is too much.
Turn on slow cooker on high, add onion, garlic, cooked beef, green bell pepper, tomato, chicken stock, tomato sauce, chili powder, cumin, Worcestershire sauce, smoked paprika, salt, oregano and black pepper. Cook for 3 hours.
Add red and black beans, cook 1 hour.
Brown the beef first on the frying pan, remember to drain excess fat if there is any.
You can use canned tomato instead of fresh tomato.
Add some extra secret ingredients to your chili to enhance the flavor if you prefer, for example chocolate, molasses or coffee. Approximately 1/2 to 1 teaspoon of one of these ingredients will be sufficient.
If you don't have red or black beans use any that you have in your kitchen pantry: pinto, black-eyed, white etc.