Chop up onion into strips. Mix balsamic and oil. Marinate with onions and mix. The longer the better.
On 13 x 9 glass dish place loin cut halfway down stuff with garlic cloves (chopped). Use tooth picks to suture back up. Onions go on top of loin.
350 degrees for 90 minutes. Cut entire thing in half long way. Should be white and wet. If not cook longer if so cut into pork chop sections.
Serve with mashed potatoes and veggies.