1. In a non-stick skillet or saucepan, melt the butter. Over high heat, add the well-washed and finely sliced leeks. Season with salt. Cook for 10-15 minutes over medium heat, covered, stirring occasionally.
2. Deglaze with a splash of Noilly Prat and continue cooking for 5-10 minutes to evaporate the alcohol and obtain a very tender leek fondue.
3. Meanwhile, heat the cream in a saucepan to reduce and slightly thicken it. Add chopped parsley and a little finely chopped garlic according to taste. Adjust the seasoning by adding pepper and a pinch of nutmeg.
4. Pour a little liquid cream into the leek fondue and mix well.
5. Pour 1/3 of the remaining liquid cream into the bottom of a gratin dish. Place 1 to 2 sheets of ravioli - depending on the size of your dish - to line the bottom of the dish like lasagna. Cover with a little leek fondue. Alternate between ravioli and leeks until all the ingredients are used, finishing with a sheet of pasta. Pour the remaining parsley cream (2/3) over the gratin and sprinkle with grated Comté cheese.
6. Bake for a few minutes (15 to 25 minutes) under the broiler in a preheated oven at 190°C (375°F). Watch the cooking process; the gratin is ready when it is well colored and golden. Serve immediately with fresh salad.