Preheat your oven to 160°C. The roasting time for this type of pork joint is 25-30 minutes per 1/2 kilo.
Peel the onions, cut in half and then slice in the direction top to tail.
Cover the pork with a good sprinkling of salt, pepper and paprika.
Place a roasting pan or casserole on your stove, turn the heat up to moderately hot and add the olive oil and butter. Place the pork in the roasting pan and brown evenly on all sides.
Remove the pork and place on a plate. Turn down the heat, add the onions and sauté slowly until glassy and slightly brown.
Pour in the chicken stock and bring to the boil. Remove from the heat, place the pork on top of the onions.
Pop into the oven and cook for 50 – 60 minutes.
Remove pork from the roasting pan and wrap in aluminium foil and a tea clothe. Leave to rest for 10-15 minutes.
Slice thinly, pour any juices which run off into the sauce and serve with a large spoonful of the onions and some of the sauce.