Heat a large frying pan over medium-high heat; cook and stir the beef in the frying pan until crumbly and no longer pink, about 5 minutes. Stir in the crushed chillies, garlic and onion; continue cooking until the beef has browned and the onion has softened and turned translucent. Add the green and red pepper and cook 5 minutes more.
While the beef is cooking, combine the kidney beans, black beans, cannellini beans, passata, passata with onion and garlic, chopped tomatoes and pumpkin puree in a large slow cooker. Season with pumpkin pie spice, chilli powder, cumin and salt. Stir in the minced beef mixture.
Cook on Low until the chilli is hot, 1 to 2 hours.