Spray a large frying pan with low-calorie cooking spray and place over a medium heat.
Add the onions and cook for 10 minutes, until soft and golden. Then add the garlic, and continue to cook for a further 1-2 minutes.
Add the peppers and cook for 5 minutes. Then add the minced beef, and cook for a further 4-5 minutes, until browned.
Add the chilli powder, smoky BBQ seasoning, paprika, and cumin. Stir everything in, and cook for 1-2 minutes.
Transfer to your slow cooker and add the chopped tomatoes, tomato puree, kidney beans, balsamic vinegar, Worcestershire sauce (or Henderson's relish), sriracha sauce, and beef stock. Stir well, then cover with the lid.
Cook on high for 3-4 hours.The chilli will be ready when the sauce is rich and thick. If the mixture is still a little runny, remove the lid, and continue to cook until reduced and thickened. Then serve!