Remove the skin of the beef and sprinkle with plenty of salt and pepper. Melt the butter in a pan on the stove and add the oil. Put the beef in to fry evenly on all sides.
Place the pre-chilled beef fillet on the puff pastry and roll it up, while squeezing the ends tightly closed. Brush the top with beaten egg and put it to bake in a preheated 392°F (200 °C) oven, for 35-40 minutes.