A good beef fillet (preferably Aberdeen Angus) of around 1kg/2lb 4oz. 3 tbsp olive oil 250g/9oz chestnut mushrooms, add some wild ones if you like 50 g / 2 oz butter 1 large sprig fresh thyme 100ml/3.5 fl oz Dry White Wine 12 slices prosciutto 500 g/1 lb 2 oz pack puff pastry, thawed when frozen a little flour, for dusting Beat 2 egg yolks with 1 tsp water
Spread half the duxelles over the prosciutto, then place the fillet on it and spread the remaining duxelles. Use the edges of the cling film to pull the prosciutto around the fillet, then roll it into a sausage shape, rolling up the ends of the cling film to tighten it. Chill the fillets while you roll out the pastry. Dust your work surface with a little flour. Roll out one third of a 500 g pack of puff pastry into an 18 x 30 cm strip and place on a non-stick baking sheet.