Season the pork ribs with salt and pepper on both sides.
Dust lightly with flour. Shake off the excess flour.
Put butter and olive oil in a skillet and turn heat to medium.
When the butter starts foaming, place the pork ribs in the skillet and brown accurately on both sides.
Add the balsamic vinegar and let it evaporate.
Add half of the stock.
Adjust density of the sauce adding more stock in case it is too dense, or more flour if it is too liquid. Serve hot.