Add the bacon to a large pan then turn the heat to medium. Gently fry until crisp with the fat rendered down, then add the bacon to a 3.5L slow cooker, leaving the excess fat in the pan.
Raise the heat slightly to medium-high then add the peppers, onion, celery and garlic. Fry until it all softens and starts to colour. This step is important not only to develop some flavour, but also to sweat out the moisture so the filling doesn't come out watery in the slow cooker. Add the beef and fry until browned, breaking up with your wooden spoon as you go. Add it all to the slow cooker.
Add the crushed tomatoes, kidney beans, tomato puree, Oxo cube, Cajun seasoning, smoked paprika, salt and pepper to the slow cooker and give it all a good stir. Use your wooden spoon to level the top so it's flat. Slice the baby potatoes to around 1/4" thick then lay the slices over the filling, working from the outside in, overlapping as you go (see video for reference). Generously season with salt and pepper, then pop the lid on and cook on HIGH for 3 1/2 hours or LOW for 7 hours, or until the potatoes are very tender.
Take the lid off, cover with cheese then add the lid back on for 5 or so mins, or until the cheese melts. If there's a considerable amount of water on the potatoes before you add the cheese, you can gently dab them with kitchen roll/paper towel to remove some. If it's just oil I typically leave it there as it's flavour.
Serve up with sour cream if desired then tuck in and enjoy!