For the roast veal roll, preheat the oven to 250°C (482°F) (fan 230°C - 446°F). Season the roast all over and fry vigorously in an ovenproof roasting pan in vegetable oil at a high temperature. Add the onion and cook till it turns translucent, then add the stock and herbs. Cook the roast in the oven on the middle shelf for 15 minutes. Reduce temperature to 200°C (392° F) (fan 180°C - 356°F) and cook for a further 1 hour 30 minutes, adding more stock if needed. Remove from oven and allow to rest. Meanwhile, filter the roasting fat out of the roasting juices through a sieve lined with kitchen paper, and remove the herbs. Combine the stock, crème fraîche and wine into a sauce, and season to taste.
While the roast is in the oven, mash or pass the potatoes through a ricer, to make a smooth, very fine purée for the noodles. Combine with cornflour, egg yolk and melted butter, season with nutmeg and salt. Roll out onto a floured work surface and cut into segments. Shape into potato noodles and cook in salted boiling water for 5 - 7 minutes, then lift out onto paper towels to drain. Melt 3 tbsp of butter in a pan over medium heat and sauté the noodles until golden brown. Alternatively, cook potato noodles from the chiller cabinet following the instructions on the packet, and then sauté them.
For the gratin, clean the carrots and cut them slightly diagonally into waferthin slices. Grease a baking dish with butter, and sprinkle with nutmeg. Arrange the carrot slices in a fan shape. Season the cream with the coriander, salt and pepper and pour over the carrots. Bake in the preheated oven (put in for baking at 200°C - 392°F) for 25 - 30 minutes until golden.
Serve from the dish or cut into carrot squares with the roast and noodles