Preheat the oven to 190°C/ Gas 5. Take the beef out of the
fridge and allow it to get to room temperature.
Mix the grain mustard with the horseradish and sprinkle in the
thyme leaves. Mix together, then rub the mixture generously over
the beef.
Season with salt and freshly ground black pepper.
Place the prepared onions and garlic in a heavy based roasting
tin and sit the beef on top. Dot the duck fat around the meat and
vegetables. Alternatively, drizzle with the oil.
Roast in the oven for approximately one and a half hours (this
will give you rare meat). Cook for a further 30 minutes for medium
or a further half an hour, if you prefer it well done.
When the beef is cooked, remove from the oven, cover with foil
and allow it to rest in a warm place for 30 minutes.
Reserve the juices from the roasting tin to make your gravy -
squeeze the softened garlic cloves into the gravy for a delicious
rich flavour.
Carve the meat and serve with crispy roasties, Yorkshire
Puddings, red cabbage, parsnips and sprouts.