Cut the cauliflower into florets and cook in boiling salted water until very tender (the blade of a knife should enter easily).
Drain the florets and divide into half. Store the rest of the cauliflower for use in other recipes, such as a gratin.
Mash the cauliflower florets with a fork to make a coarse purée. Stirring, add cream, two whole eggs, salt, pepper and grated nutmeg.
Finally, add two good tablespoons of grated Parmesan. Mix well.
Bring a large pot of water to a boil. Salt and add the lasagne sheets. Let them cook for 2 or 3 minutes (just long enough to soften them).
Then, take them out with a slotted spoon and let drain flat on a cloth, taking care not to overlap.
Preheat oven to 400° F.
Dice the Ile de France Roquefort.
Arrange a first layer of lasagna in the bottom of a baking dish and cover with a third of the cauliflower puree.
Scatter half of the diced Ile de France Roquefort. Repeat again: a layer of lasagne, the second third of the puree and the remaining diced Ile de France Roquefort. End with the sheet of lasagna covering the final third of the cauliflower puree.
Sprinkle generously with grated parmesan cheese and walnuts. Bake 25 to 30 minutes and serve hot. Enjoy!