In a large mixing bowl, combine the pumpkin puree, grated Parmesan cheese, salt, ground nutmeg, and ground cinnamon. Mix until well combined.
Gradually add the flour to the pumpkin mixture, stirring continuously, until a soft dough forms. If the dough is too sticky, you can add a little more flour until it becomes workable.
On a floured surface, knead the dough gently for a few minutes until it comes together. If the dough is too sticky, you can sprinkle more flour as needed.
Divide the dough into small portions and roll each portion into a rope about 1/2 inch thick.
Cut the ropes into bite-sized pieces and press each piece lightly with a fork to create ridges (this helps the sauce adhere better). To bind the dough further, beat an egg yolk in a separate bowl and brush it lightly over the gnocchi.
Bring a large pot of salted water to a boil. Drop the gnocchi into the boiling water and cook for 2-3 minutes, or until they float to the surface. Remove them with a slotted spoon and place in a large bowl.