Preheat the oven to 220ºC. Cut down the middle of each salmon fillet lengthways on the flesh side, going about three-quarters of the way through to make a pocket. Finely grate the Parmesan, beat with the crème fraîche, then mix in the prawns.
Rub a large deep sturdy tray with a little olive oil and place on a low heat on the hob. Peel and finely slice the garlic, add to the tray with the spinach, season, stir until just wilted, then turn the heat off. Nestle in the salmon fillets, divide and spoon the prawn mixture into the pockets, then sprinkle with black pepper. Drape one rasher of pancetta over each fillet. Rub the rosemary sprigs with a little oil and place one on each piece of salmon. Cook in the oven for 15 minutes, then serve.
7 Ways by Jamie Oliver is published by Penguin Random House © Jamie Oliver Enterprises Limited (2020 7 Ways).