Preheat oven to 180°C (350°F/Gas 4). Peel the butternut squash, cut into sections and remove the seeds and threads using a small sharp knife. Cut into slices approx. 1.5 cm (½ inch) thick. Arrange on a baking sheet lined with baking paper and sprinkle with salt. Bake in the middle of the oven for approx. 30 minutes until done. Press them through a potato ricer or mash until smooth with a hand blender. Using a fork, as it can get sticky, add the flour and egg yolk and season with nutmeg, pepper and salt. Be careful, this mixture will always be a little sticky. Do not add too much flour, as the gnocchi will become tough. You will have to become a little practised at rolling these gnocchi: work on a spacious surface dusted with flour and with floured hands. Quickly roll the dough into thin ropes. Cut into small cushions with a floured knife. Save on a baking sheet lightly dusted with flour until used. Bring a large pan of water to a boil. Add the salt and cook in small quantities for 3 to 4 minutes until done. Sprinkle with grated parmesan cheese, and roasted pumpkin seeds.