1.Preheat oven to 160°C (140°C fan-forced).
2.Brush beef with 1 tbsp of the oil; sprinkle with pepper. Heat 1 tbsp of the oil in a large shallow flameproof baking dish. Cook beef, uncovered, over high heat until browned all over. Roast, uncovered, in oven about 1½ hours or until cooked as desired.
3.Meanwhile, heat remaining oil in another large flameproof baking dish. Cook potatoes, stirring over high heat until browned lightly. Add pumpkin and kumara, place dish in oven with beef. Roast, uncovered, about 35 minutes or until vegetables are browned.
4.Place beef on vegetables, cover with foil and return to oven to keep warm. Drain juices from beef baking dish into a medium saucepan. Add brandy and bring to the boil. Add stock and blended cornflour and water; stir until sauce boils and thickens slightly. Stir in chives; pour into medium heatproof jug.
5.Serve beef and vegetables with sauce.