Ingredients: at least 500g/1lb2oz fresh porcini, or other boletus (ideally twice that quantity) 275g/10oz parma ham, sliced very finely white lasagne sheets, ideally fresh, but dried can be used (enough to make at least 3 layers in an 20cmx25cm/8x10in baking tray) at least 250g/9oz fresh parmesan truffle oil (optional) butter For the bé chamel: 500ml/17fl oz hot milk 50g/2oz butter ...