Pre-heat the oven to approximately 120 - 130° Celsius.
Use large casserole/pot with the lid on and add some oil on the bottom (I prefer rapeseed oil). I also cut the stalk off the chilli as I like hot foot, but for those who prefer 'warm' food I would leave the chilli whole with the stalk on.
Put the joint of meat in with one or more of; roughly chopped onions (red, white or shallots), 1 - 2 quartered gloves of garlic, a chilli pepper - I prefer green chillies as I prefer the slightly bitter taste, but red chillies are fine too.
I also cut the stalk off the chilli as I like hot foot, but for those who prefer 'warm' food leave the chilli whole with the stalk on.
Then put a bit more oil on the meat and season with salt, pepper and perhaps some Cajun mix or hot paprika, should you wish to do so.
Cook the joint, at 120-130°C, for 4 - 5 hours and to make it extra tender (and if you have time) leave the joint in pot with the lid on (having taken it out the oven) over night and cook it, again at 120-130C, for another couple of hours the next day.
Having done processes 1 to 3 (or 1 to 4, if there's time) the meat should just fall away from the bone and can either then be used as a roast joint in its own right, or the meat can be sliced/pulled apart and used in stir-fries, pasta, burgers etc., or allowed to cool for cold meat in sandwiches.