Divide dough into 4 portions. Work with one portion at a time, keeping the others covered with plastic film. Flatten the dough out onto a lightly floured surface and roll out from centre to the outer edges. When the dough is about 5mm thick, fold it in half and roll out again to the same thickness. Repeat this process 3 more times - it will activate the gluten and ensure the pasta is smooth and soft once cooked.For the final roll try to make the rolled out sheet about 2mm thick and more oval in shape. Dust lightly with flour during the process if the dough sticks to the surface or pin. Using a sharp knife, cut the sheet into a rectangle and leave uncovered on a wooden cutting board to air-dry slightly. Repeat with the other portions.
Bring a large pot of water with 1/2 tsp sea salt to the boil. Place pasta sheets in the pot and cook for about 3 minutes or until the pasta is just al dente.
In the meantime, heat remaining butter in a saucepan until bubbling. Add sage leaves, allow to crisp up. Remove onto paper towel to drain excess oil. Add in hazelnuts and spinach into the same pan. Stir well until the spinach is wilted.
Place pumpkin back on the heat to warm through. Drain pasta and cut sheets into squares.
To serve place 1 tbsp of pumpkin mash on the bottom of the plate. Sprinkle with pecorino. Place 1 lasagne square over the pumpkin. Layer with 1 tbsp pumpkin mash, 2 tbsp spinach mix, 2 sage leaves and pecorino. Repeat the layering once more and then again on the top of the sheet. Serve with freshly ground black pepper.