Rib of beef with porcini, tarragon and port gravy

Method

1. Preheat the oven to 190°C/fan 170°C/gas 5. Rub the beef all over with oil and season. Put the onions in a big roasting tin, then sit the beef on top. Pour in half the stock, then add 4 tarragon sprigs. Roast for 25 minutes, then turn the heat to 170°C/ fan150°C/gas 3½ and cook for 1 hour 30 minutes for medium rare (add 20 minutes for medium). If using a meat thermometer, it should read 55°C in the middle for medium rare (65°C for medium). Don’t let the tin dry out – keep adding splashes of stock.
2. Meanwhile, soak the porcini in 300ml boiling water for 30 minutes, then drain, chop and set aside, reserving the soaking juice.
3. Remove the beef from the oven and put it on a lipped board, very loosely covered with foil.
4. Strain the juices from the tin, then skim off the fat, reserving 2 tbsp. Heat the fat in a pan, then stir in the flour and cook until it smells biscuity. Add the 150ml port, stirring, and bubble until the alcohol smell has gone. Strain in the roasting juices and porcini juice, stirring to a glossy gravy that just coats the back of a spoon (add the rest of the beef stock if you wish). Stir in the porcini, then add an extra splash of port, the vinegar and the remaining tarragon, chopped. Check the seasoning, then serve with the beef.