truffle oilor if possible a little shaved white truffle
Melt 50 g/2 oz of the butter, add the flour and blend in well. Add the milk, which has been previously heated, a little at a time beating well with a balloon whisk. Cook the porcini in the olive oil and add to the béchamel. Stir in the Parma ham. Add the cream and parsley, season, and bring to the boil. Turn off the heat.
Butter a gratin dish and cover the bottom with a layer of pasta, then spread over a layer of béchamel, dot with butter and sprinkle with some Parmesan cheese. Continue the process making layer after layer, finishing with a béchamel layer and a sprinkling of Parmesan cheese.
Cook in an oven preheated to 220°C/425°F/gas 7 for 20 minutes. Serve with a little truffle oil splashed on top or, better still, with shavings of white truffle, and a little Parmesan cheese.