Prepare the pumpkin: Peel the pumpkin and cut into uniform pieces. Place on a baking tray lined with parchment paper and roast in a preheated static oven at 170°C (338°F) for 20-30 minutes until tender.
Make the filling: While still warm, mash the roasted pumpkin with a potato masher. Add crushed amaretti biscuits, chopped Mantuan apple mustard, grated Parmesan, lemon zest, nutmeg, salt, and black pepper. Mix until you get a dry, compact filling.
Prepare the pasta dough: On a clean surface, heap the flour and make a well in the center. Crack the eggs into the well, add a pinch of salt, and gradually incorporate the flour with a fork. When the dough starts to come together, knead for about 5 minutes until smooth and elastic. Form a ball, wrap in cling film, and refrigerate for 30 minutes.
Roll out the pasta: Flatten the dough ball with your hands, dust with flour, and pass it repeatedly through a pasta machine to obtain thin sheets.
Form the tortelli: Cut the pasta sheets into 5-6 cm squares using a fluted pastry wheel. Place a small amount of filling in the center of each square. Fold the dough over to form a half-moon shape and press the edges firmly to seal, pinching the ends to resemble a candy shape.
Cook the tortelli: Bring a large pot of salted water to a boil. Cook the fresh tortelli until they float to the surface, which will take only a few minutes.
Prepare the sage butter sauce: While the tortelli cook, melt butter in a pan with fresh sage leaves until fragrant.
Serve: Drain the tortelli and toss them gently in the sage butter sauce. Plate and generously sprinkle with grated Parmesan. Garnish with pumpkin seeds and crumbled amaretti biscuits for color and crunch.