In a large mixing bowl, combine the pumpkin puree, flour, egg, salt, nutmeg, and black pepper. Mix until a soft dough forms, being careful not to over-knead.
Lightly flour a clean work surface and turn the dough out onto it. Divide the dough into four equal portions.
Roll each portion into a long rope, about ½ inch thick. Cut the ropes into 1-inch pieces to form gnocchi. You can create ridges on the gnocchi by rolling each piece over the back of a fork.
Bring a large pot of salted water to a gentle boil. Carefully add the gnocchi in batches, cooking them until they float to the top (about 2-3 minutes). Use a slotted spoon to remove them and transfer to a plate.
In a large skillet, melt the butter over medium heat. Once melted, add the sage leaves and sauté for 2-3 minutes until the butter is golden brown and the sage is crispy.
Add the cooked gnocchi to the skillet and gently toss to coat them in the sage butter. Allow them to cook together for another minute.
Remove from heat and serve immediately, garnished with grated Parmesan cheese if desired.
Notes
Serve the gnocchi in a shallow bowl, drizzled with sage butter and garnished with crispy sage leaves and Parmesan.