Grate the Parmigiano Reggiano cheese finely, and set to one side.
Heat the olive oil in a frying pan and add the halibut fillets. Cook them over a medium heat for five or six minutes, turning once. Add the prawns and two sprigs of lemon thyme and cook for a further two minutes. Season with a little salt and pepper to taste.
Meanwhile, make the sauce. Put the cream into a saucepan and heat gently, whisking with a small whisk. Add the white wine, then the grated Parmigiano Reggiano, stirring until melted and smooth.
Serve the fish with the prawns and pour the sauce on top and garnish with the remaining thyme sprigs.
Cook’s tip: Use any firm fillets of fish instead of halibut – salmon or monkfish would work well too.