3 tablespoons extra virgin olive oil (EVOO), divided
1 boneless pork lion (4 1/2 pounds)
Salt and freshly ground black pepper
8 sprigs rosemary, 7 whole and 1 chopped, divided
2 slices pancetta (each about 1/4-inch thick), diced
1 medium onion, chopped
1/4 cup white balsamic vinegar
2 tablespoons butter
2 tablespoons flour
1/2 cup white wine
1 1/2-2 cups chicken stock
A few dashes of Worcestershire sauce
Pre-heat the oven to 400ºF.
Place a large skillet over high heat with two turns of the pan of EVOO, about 2 tablespoons. Season the pork loin with salt and pepper and sear in the hot skillet until brown on all sides. While the loin is searing, set a rack in a roasting pan and place the whole sprigs of rosemary on the rack. Transfer the seared pork loin to the rack and reserve.
Return the skillet over medium heat with one more turn of the pan of EVOO, about 1 tablespoon, and add the pancetta. Cook until crispy and golden brown, about 5 minutes, then add the onion and chopped rosemary to the pan and cook until the onions are tender, about 5 minutes. Add the balsamic vinegar to the pan and cook until reduced, about 2 minutes, then season the mixture with salt and pepper. Top the seared pork loin with the pancetta-onion mixture and roast until done to your liking, about 1 hour (internal temperature should be 140ºF for medium doneness).
When the pork is ready, transfer it to a cutting board and tent with foil to rest. Place a medium skillet over medium heat with the butter. When the butter has melted, sprinkle the flour over top and cook for about 1 minute. Add the white wine to the pan and whisk to incorporate. Pour off the pan juices from the roasting pan into the skillet, removing the rosemary sprigs (the rosemary can be discarded or saved for garnish on a serving platter). Add the Worcestershire and stock the pan and bring up to a bubble. Simmer the gravy until thickened, about 2 minutes, and season with salt and pepper.