In a large bowl, combine the pumpkin puree, flour, egg, salt, and chopped sage. Mix until a dough forms.
Turn the dough out onto a floured surface and knead gently until smooth. Divide the dough into four portions.
Roll each portion into a long rope, about 1/2-inch thick. Cut the ropes into 1-inch pieces to form the gnocchi.
In a large pot of boiling salted water, cook the gnocchi in batches until they float to the surface, about 2-3 minutes. Remove with a slotted spoon and transfer to a plate.
In a large skillet, melt the butter over medium heat. Add the cooked gnocchi and sauté until lightly browned, about 2-3 minutes.
Serve the gnocchi with grated Parmesan cheese on top.