Place the tripe and kneecap (bones and all) in a pot. Cover with water and add a tablespoon of vinegar.
Boil on the stovetop for 10 minutes.
Drain the tripe and kneecap, and rinse well under the tap.
Place the tripe and kneecap in the slow cooker.
Pour in enough broth to cover.
Cook on HIGH for three hours.
Scoop out the tripe and kneecap.
They will still be tough at this stage so use a sturdy knife. Cut the tripe into strips about an inch wide.
Separate the kneecap bones from the meat and tendons. Cut the meat and tendons into strips.
Take a cup of broth from the slow cooker and stir the tomato paste in it.
Put the tripe and kneecap (including the bones) back into the slow cooker.
Add the chorizo, garlic, onion, bay leaf, oregano, chilies and diluted tomato paste.
Season with salt and pepper. Stir.
Set the slow cooker to LOW and cook for another 12 hours.
Heat the olive oil in a pot. Add the carrot cubes, diced bell peppers, chickpeas and olives.
Cook over medium heat until the carrot cubes are cooked but still a little crisp.
Sprinkle with salt and pepper.
Fish out the bones from the slow cooker and discard.
Pour the contents of the slow cooker into the pot with the vegetables. Stir.
Cook just until simmering.
Serve your slow cooker callos with rice or bread.