AT A GLANCE
A rib roast is an investment - take care to rest the meat well to make the most of it.
|01||Combine oil, rosemary, mustard and anchovies in a non-reactive dish, add beef, turn to coat, cover and marinate at room temperature (1 hour).|
|02||For potato gratin, preheat oven to 190C. Whisk cream and garlic in a bowl to combine. Peel and thinly slice potatoes on a mandolin into the cream, tossing to coat as you go to prevent discolouration, season to taste and arrange in even layers in a buttered 30cm x 30cm oven dish. Season with freshly ground black pepper and a grating of nutmeg, cover with baking paper then foil and bake on lowest rung of oven until a knife pierces potato easily (45 minutes to 1 hour). Uncover and cook until golden (30 minutes). Keep warm.|
|03||Meanwhile, place beef on top of onions in a roasting dish and roast on top shelf until medium-rare (1½ hours). Set beef aside loosely covered with foil to rest (30 minutes), then serve with gratin and mustard.|