Potato Gratin With Mustard Beef Fillet

Heat the cream, milk, butter, nutmeg and garlic in a medium saucepan until just below boiling point.
Strain cream mixture into a large bowl and discard the garlic.
Slice the potatoes as thinly as possible and add to the cream mixture. Stir well to ensure potatoes are evenly coated.
Preheat the oven to moderately hot (200°C/180°C fan-forced).
Layer the potato mixture in a greased, shallow ovenproof dish (2litre/8-cup capacity). Cover with greased foil and bake in moderately hot oven for 40 minutes.
For the mustard beef fillet, heat the oil in a small flameproof baking dish. Add the beef and cook over a high heat until browned all over. Remove from the heat; spread the beef with mustard and sprinkle with salt. Place beef on a wire rack in same dish. Pour the wine and stock into dish. Roast the beef, on the top shelf of the oven, for about 35 minutes or until cooked as desired. Transfer the beef to a plate, cover with foil; stand for 15 minutes.
Add stock to the pan juice in the baking dish with blended cornflour and water. Bring to the boil, simmer, uncovered, until the sauce thickens slightly; strain into a serving jug.
Remove foil from the potatoes, top with cheese; bake, uncovered, for further 20 minutes or until potatoes are tender.
Cut potato gratin into pieces, serve topped with thickly sliced beef drizzled with sauce