This calls for a good chunk of beef, like an aged rib-eye stripped of the outer fat, leaving you with a nicely marbled eye of meat which should melt in your mouth.
- 1 rib-eye of beef, off the bone, weighing about 1-1.5 kg, tied
- Salt and freshly ground black pepper
- Vegetable oil or dripping for roasting
- 2tbsp chopped parsley
- 1tbsp chopped thyme leaves
- 12tbsp chopped rosemary
- 1tbsp grain mustard
- 4 large onions, peeled and cut into 3 thick slices
- Pre-heat the oven to 220ºC/430ºF/.
- About 10 minutes before you put the beef in, heat a couple of tablespoons of vegetable oil or dripping in a large roasting tray until it’s beginning almost to smoke (you can do this on top of the stove).
- Season the rib-eye with some sea salt and pepper and roast for 10 minutes, then turn it over to seal the meat and keep the juices in.
- Remove the tray from the oven and take the beef out of the roasting tray.
- Spread it with the grain mustard on all sides, mix the herbs together and rub them all over the beef.
- Put the onions in the middle of the roasting tray and put the beef on top, then return to the oven.
- Allow 30 minutes per kilo for rare; 45 minutes for medium to well done. Baste the meat regularly with the pan juices.
- Once cooked remove the beef from the tray and leave to rest on a plate for 10-15 minutes.
- Add a couple of tablespoons of water to the roasting tray and put on a medium flame on top of the stove.
- Stir with a spoon a couple of times to remove any residue from the bottom of the pan, then transfer the onions and any juices to a blender.
- Blend to a coarse consistency, season with salt and pepper if necessary then transfer to a serving bowl.
This sort of roasted onion soubise goes particularly well with the beef.
Serve the beef, preferably still warm, sliced into 1 cm slices with the horseradish potatoes and onion sauce served separately.