Buy puff pastry!!
Fine chopped mushroom, shallots, couple of sprigs of thyme, good slug of brandy....fry.
Lay overlapping parma ham slices on clingfilm. Cover with layer of mushroom mix. (remove thyme sprigs)
Sear loin. Lay on mushroom mix, roll up clingfilm to make a sausage, put in fridge to firm up.
Roll out pastry, put 'sausage' (minus cling film) in pastry, seal, eggwash, bake in hot oven til golden.