1. Wash the Jerusalem artichokes well and steam them until they are soft enough to be mashed with a fork. Then peel them and mash them.
2. Prepare the béchamel: In a small saucepan melt the butter, add the flour and mix well. Gradually pour the milk, mixing and being careful not to form lumps. Grate a bit of nutmeg, add a pinch of salt and cook stirring constantlyuntil it has thickened.
3. Once the Jerusalem artichokes have cooled a bit, mix them with ricotta, artichoke cream, beaten egg, 3 tablespoons of Parmesan, a pinch of nutmeg, salt and pepper.
4. In abundant salted water, blanch the pasta for a few minutes, then drain them on a clean cloth.
5. Place a thick béchamel sauce on a baking sheet and place the pasta on top. With the ricotta mixture obtained, fill a sac-a-poche and fill the pasta.
6. Cover the pasta with the rest of the bechamel and sprinkle abundantly with grated Parmesan.
7. Cover with aluminum paper and bake in preheated oven at 180 ° for about 15 minutes. Then increase the oven temperature to 200°C or set the upper grill function, remove the aluminum and continue cooking for another 3-5 minutes, until is browned.
Allow to cool for 5 min and serve.