Preheat the oven to 180°C.
Thinly slice the white onion, leeks, parsnips and carrots in to rounds.
Heat the olive oil in a frying pan and add the white onion, leeks, carrots and parsnips. Season with salt and pepper.
Brown the vegetables, add a little water, cover and cook for 20 minutes over a low heat.
Cut the sweet potato into cubes.
Bring some salted water to the boil in a large saucepan, add the sweet potato cubes and cook for 15 minutes. Drain.
Place half the onion-carrot-leek-parsnip mixture and half the sweet potato in a gratin dish. Drizzle with ALSACE LAIT crème fraîche from Alsace for pouring. Sprinkle with curry powder.
Crumble on half the goat's cheese and repeat. Sprinkle with grated Emmental cheese.
Bake in the oven for 45 minutes.
Place a generous portion of the gratin on the plates and sprinkle with the curly parsley.