Preheat the oven to 170C.
Season the beef joint all over with your favourite flavourings, I like to use salt, pepper, garlic powder and mustard powder, brought together with a little olive oil. Carefully fry the meat all over in a heavy pan, before transferring to the oven.
Put the potato peelings in a tied up clean dishcloth. After 30 minutes parboil the potatoes in salted water along with the peelings. After 10 minutes drain thoroughly and discard the peelings.
Remove the beef from the oven, add the potatoes and onions to the baking tray and baste well. Return the beef to the roasting dish, on top of a rack over the potatoes if you have one.
Roast for a further 45m or until your beef is done. When it's out crank the oven up as high as it will go and continue to cook for a further 15 minutes or until the potatoes are as crisp as you like them. Serve sprinkled with sea salt.