Add a thin covering of groundnut (peanut or canola) oil to a heavy based frying pan and place over a medium heat.
Season the beef rib with salt.
When the pan is almost smoking, add the beef rib and brown on all sides.
Place the beef rib in a large roasting tin and roast slowly in the pre-heated oven for approximately 5 hours or until the centre of the meat reaches 55 degrees Celsius (130F) – this will give you a medium rare joint of beef.
If you would like the meat more cooked, then leave until the thermometer reads 60 degrees Celsius (140F).
When the meat reaches the required temperature, remove the tin from the oven and leave it to rest for half an hour.
Preparing the Sauce
Melt the butter in a frying pan and sauté the shallots until they are a pale golden colour.
Add the white wine and simmer the sauce until you have 40 ml left.
Add the Dijon mustard and whisk to incorporate.
Add the beef stock and 1 tbsp of Marsala wine.
Simmer for 2 minutes and set aside.
When the beef has rested, reheat the sauce and stir in the chopped tarragon. Remove the bone and carve the meat in thick slices.
I serve this dish with fondant potatoes and lightly grilled asparagus with parmesan, but it works very well with roasted mixed vegetables.