Preheat the oven to 220°C.
Season the pork with salt, pepper, and lemon zest.
Mix parmesan, pork mince, livers, onions, herbs, soaked bread, pine nuts, and sultanas in a bowl.
Spread filling on the loin, layer with mortadella, roll tightly, and tie with kitchen string.
Rub the meat with olive oil and salt.
Place carrots, onion, wine, Vin Santo, and 125ml water in a tray with the pork on top.
Roast at 220°C for 30 minutes, then reduce to 150°C for three hours.
Fry par-boiled potatoes in oil until they begin to brown.
Add rosemary and garlic to the potatoes and cook until crisp.
Serve the sliced porchetta alongside the sautéed potatoes.