Ingredients

Step by step

1. Start with the stuffing. In a heatproof bowl, cover the porcini with boiling water. Stand for 30 minutes or until soft. Drain, reserving the liquid, then squeeze and finely chop.
2. Melt the butter in a large frying pan. Add the shallots, garlic and thyme, plus a pinch of salt; cook gently for 5 minutes until soft. Add the chestnut mushrooms and porcini; cook for 10-15 minutes, until they're soft and no liquid remains. Cool; stir in the parsley.
3. Preheat the oven to 220°C, fan 200°C, gas 7. Make a slit lengthways along the beef fillet without cutting all the way through (leave about 2cm at the bottom). Open up the beef like a book, flattening it out slightly. Season well, then fill the middle with the stuffing. Dot the blue cheese over the top, then bring the fillet around the filling so it is sealed in.
4. Use the back of a knife to stretch the pancetta slices. Lay them on a sheet of baking paper, slightly overlapping, to form a rectangle the same length as the fillet. Season with pepper and add the chopped leaves from 2 thyme sprigs. Lay the fillet at the long edge of the rectangle and roll the pancetta slices around it, using the paper to help, so the stuffing is enclosed. Tie the fillet every 2cm with butcher's string so it forms a sausage shape. Tuck the bay leaves under the string.
5. Put the fillet in a large roasting tin, with the garlic cloves and remaining thyme sprigs. Drizzle with olive oil; roast for 30-35 minutes for rare to medium-rare, or 40 minutes for medium. Remove the beef from the tin, cover with foil; leave to rest for 15-20 minutes.
6. Put the tin on the hob, add the red wine and sugar; bubble for a few minutes, stirring, until thick. Add the stock and the strained porcini liquid; bubble until slightly thickened. Season; stir in any resting juices. Strain into a gravy jug. Thickly slice the beef and serve with the gravy.