1Heat olive oil in a large sauté pan over medium high heat. Once hot, add the sausage and cook, while stirring and breaking up with the back of your spoon. Toss in the onion, garlic, bay leaves and rosemary, and cook until the meat is browned off and the onion is tender, about 8 minutes.
2Add ½ cup white wine and cook until half of the liquid has reduced. Remove from heat and stir in the parsley. Remove the mixture to a bowl to cool.
3Heat oven to 425 degrees.
4Meanwhile, while filling is cooling, butterfly your pork loin by cutting through the roast lengthwise, almost all the way through, but leaving 2 inches, so it can open like a book. Open up the pork and lay flat, then pound the pork with a meat mallet until it’s roughly 1 ½ inches thick. (You can also ask your butcher to do this for you.)
5Season the pork on both sides with salt and pepper.
6Combine the ¼ cup olive oil, fennel pollen, garlic, and thyme together in a small bowl. Rub half of the mixture on one side of the pork.
7Pat the cooled sausage down across the pork in an even layer. Roll it up tightly like a burrito. Using butcher’s twine, tie at 1 ½ inch intervals.
8Rub the outside of the pork all over with the rest of the olive oil fennel rub. Place the roast fat side up on a rimmed sheet tray, add beer to the bottom of the pan along with any juices left over from the skillet and place in the oven.
9Roast the pork for 30 minutes, then lower the heat to 350 degrees.
10Continue roasting for 40 minutes more, until golden and crisp on the outside, and an instant read thermometer reads 145 degrees.
11Remove roast from oven and allow the roast to rest for 20 minutes before removing kitchen twins and slicing.