Porchetta is a slow-roasted shoulder or belly of pork with crispy crackling which is commonly sold wrapped in paper parcels from roadside vendors throughout northern Italy. Irresistible as it is, slow roasting a joint for a speedy weeknight dinner is not an option. Instead, this quick version borrows the recipe for porchetta's aromatic stuffing, which is rubbed into a butterflied pork loin wrapped up in salty prosciutto. Serve it with thinly sliced roast potatoes liberally sprinkled with Parmesan cheese and a fresh watercress salad – dinner is served.
Preheat the oven to 200 degrees. Layer the potato slices and onion across the base of a large baking tray. Sprinkle generously with Parmesan cheese and season with sea salt and ground black pepper. Place the rosemary, sage, fennel seeds, garlic, lemon zest in a food processor and blitz until finely chopped.
Using a sharp knife, butterfly the pork loin. To do this, lie the loin flat and make a cut into the side so that it can be opened like a book. Sprinkle with the chopped herbs. Roll up the pork and wrap tightly with the prosciutto slices.
Place the wrapped pork on top of the potatoes in the roasting tray and roast in the oven for 35 minutes or until the pork is cooked through and golden and the potatoes are crispy. Remove from the oven and slice the pork into 1cm thick medallions.
Whisk together the oil and vinegar in a bowl and season with sea salt and ground black pepper. Toss the watercress in the vinaigrette until coated and serve with the pork and potatoes.