First, make the Marmite butter. Beat the butter with the Marmite until completely combined, then mix in a large pinch of sea salt. Chill until needed. Can be made up to a day ahead.

Heat the oven to 220C/200C fan/gas 7. Season the beef fillet well. Heat the butter in an ovenproof frying pan until sizzling, and brown well all over – this should take about 10 mins. When it’s well browned and has a crust, move the beef to one side of the pan and lay the cabbage, cut-side down, in the other side. Press down on the cabbage to sear it, then baste with some of the butter in the pan. Put the pan in the oven and roast, turning the beef fillet every 5 mins or so. The beef will be cooked rare in 15 mins, 20 mins for medium-rare, or 25 mins for medium. When the beef is cooked to your liking, remove from the pan to a board, and leave to rest for 10 mins. Return the cabbage to the oven while the beef rests and you make the mash.

Tip the potatoes into a pan of cold salted water, bring to the boil, then reduce the heat and simmer for 10-12 mins until cooked through. Drain. Tip the milk or cream into the saucepan and heat, add the potatoes and mash with a potato masher, then beat in half the Marmite butter.

Carve the beef fillet into thick slices, drizzle over the resting juices and serve with the mash, charred cabbage and the remaining Marmite butter on the side.