Roast beef & Yorkshire pudding is one of the best-known British Classics. And for good reason: when it's done properly, it's fantastic!
You really need good quality beef for this. I generally use rib, but sirloin or ribeye are fine too. A good layer of fat on it won't hurt. First thing to do is preheat the oven to 230° C (445° F), and then season the beef with the salt, pepper and mustard. Prepare a roasting tin by placing slices of onion, celery and carrot in a single layer, and then pop the beef on top. Pour in a centimetre (half an inch) of boiling water, and put the whole lot into the oven. After 20 minutes, turn down the temperature to 180° C (356° F) for the remaining time. Use the chart below to calculate your cooking time:
Rare - 11 mins per 450g / pound
Medium - 14 mins per 450g / pound
Well done - 16 mins per 450g / pound
A better way to work out the cooking time is stick a meat thermometer into the thickest part of the beef. Note that the beef needs to be rested for 20 - 30 minutes after coming out of the oven, and its internal temperature will continue to rise.
Rare - out of the oven: 48 - 52°C (118 - 126° F). After resting: 55 - 60°C (131 - 140° F)
Medium rare - out of the oven: 55 - 59°C (131 - 138° F). After resting: 61 - 65°C (142 - 149° F)
Medium - out of the oven: 60 - 66°C (140 - 151° F). After resting: 66 - 70°C (151 - 158° F)
Once the meat is out of the oven, loosely tent it in foil, and turn the oven up as high as it will go.
Spoon the mixture into tins, and put in the oven for 15-20 minutes. Do not open the oven door during this time.
A few teaspoons of flour to thicken the gravy.