at least 500g/1lb 2oz fresh porcini, or other boletus (ideally twice that quantity)
white lasagne sheets, ideally fresh, but dried can be used (enough to make at least 3 layers in an 20cmx25cm/8x10in baking tray)
50g/2oz plain flour
freshly ground black pepper
pinch nutmeg
salt
truffle oil (optional)
butter
50g/2oz butter
500ml/17fl oz hot milk
at least 250g/9oz fresh parmesan
275g/10oz parma ham, sliced very finely