Beef a good beef fillet (preferably Aberdeen Angus) of around 1kg/2lb 4oz
3 tbsp olive oil
250g/ 9oz chestnut mushroom, include some wild ones if you like
50g/ 2oz butter
1 large sprig fresh thyme
100ml/ 3½ fl oz dry white wine
12 slices prosciutto
500g/1lb 2oz pack puff pastry, thawed if frozen...