Preheat the oven to 300 degrees F. Prepare a large roasting pan with a roasting rack placed inside. Set aside.
To make the herb filling for the porchetta, combine all the ingredients (except the pork loin and pork belly) in a bowl and mix to combine. Set aside.
To trim the pork belly, lay the pork belly skin-side down on a cutting board (or two!). Place the pork loin on to the thinner side of the pork belly and roll the belly tightly around the loin. Use a sharp knife to trim the pork belly where the pork belly meets. Unroll the pork belly from the pork loin and set aside.
Butterfly the pork loin using a sharp knife, then spread 1/3 of the herb filling evenly across the pork loin. Roll the pork loin back up and set aside.
Lay the pork belly skin-side up and use a very sharp knife (or razor) to score the skin horizontally. Score the pork belly 2 to 3 cm apart and only ½ cm deep. Continue this across the whole pork belly.
Flip the pork belly so that it is skin-side down on a cutting board again and top with the remaining 2/3 of the her filling. Spread it out evenly across the pork belly from edge to edge.
Place the pork loin back onto the pork belly and roll the pork belly around the pork loin again, making the roll as tight as possible.
Tie the porchetta using several pieces of butcher’s twine then place seam side down on the roasting rack in the roasting pan. Sprinkle the top of the porchetta with about 1 teaspoon of sea salt to get a crispy crust.
Bake the porchetta in the center of the oven from anywhere between 3 to 5 hours, depending on the thickness of the porchetta. The porchetta that I made took just under 5 hours to fully cook.
Drain the fat from the pan after the first 2 hours of cooking, then continue to drain every hour. This will avoid the fat from smoking and spattering all over the oven.
While the porchetta is cooking, make the Salsa Verde. Simply combine all the Salsa Verde ingredients in a food processor and pulse until combined and all the herbs are finely chopped. Place in a serving bowl and top with additional olive oil for garnish.
When the internal temperature of the pork reaches 155 degrees F, increase the oven heat to 400 degrees F and continue to bake for 30 minutes, or until fully cooked. This heat at the end of cooking will crisp up the skin. If you would like crispier skin, broil on high for 2 to 3 minutes, watching the skin closely so that it does not burn.
Remove the porchetta from the oven and loosely cover with foil. Let rest at room temperature for 30 minutes before removing the butcher’s twine, slicing and serving with the Salsa Verde. Enjoy!