- 1/4 cup extra-virgin olive oil
- 1 yellow onion, thinly sliced
- 1 fennel bulb, cored and thinly sliced, 2 tablespoons fronds chopped and reserved
- 2 pounds sweet Italian sausage, casings discarded
- 2 tablespoons fennel seeds
- 2 tablespoons chopped rosemary
- 6 garlic cloves, thinly sliced
- 1 tablespoon pepper, plus more for seasoning Kosher salt
- 2 eggs, beaten
- 4 medium red onions, peeled and halved
- One 5-pound, boneless pork shoulder, butterflied 1 inch thick (roughly a 10-by-14-inch rectangle)—have your butcher do this
- In a large skillet heat 2 tablespoons of the oil until shimmering. Add the yellow onion and sliced fennel and cook over moderate heat, stirring occasionally, until soft (about 10 minutes). Add the sausage, fennel seeds, rosemary, garlic and the 1 tablespoon of pepper and cook, breaking up the meat, until the sausage is browned (about 5 minutes). Season with salt. Transfer the mixture to a bowl and let cool. Stir in the eggs and fennel fronds.
- Preheat the oven to 350°. Place the red onions in a large roasting pan. Arrange the pork on a work surface and season with salt and pepper. Spread the sausage mixture over the pork, leaving a 1-inch border all around. Starting at a long side, roll up the pork and tie with kitchen twine at 1-inch intervals. Rub with the remaining 2 tablespoons of oil and place on top of the red onions. Roast the pork for about 2 1/2 hours, basting occasionally with any pan juices, until an instant-read thermometer inserted in the center of the meat registers 160°. Transfer to a cutting board and let rest for 15 minutes.
- To serve, discard the strings. Cut the pork into 1-inch-thick slices and serve with the red onions. Suggested Pairing Red wines from Italy’s northern Trentino region tend to have very concentrated fruit flavors and high acidity, excellent with over-the-top meat dishes like this pork shoulder.