Steam the pumpkin for 20 minutes, or until very soft and tender.
Using a potato masher, mash the steamed pumpkin to a smooth purée. Line surface with kitchen paper and spread pumpkin purée over before patting dry to ensure you remove as much moisture as possible. In a bowl or food processor, mix the pumpkin purée, ricotta, grated parmesan, the egg, ¼ tsp salt, and some black pepper. Stir well to combine, then add the flour and use a wooden spoon to mix to a soft dough taking care not to "overmix". Turn out the dough onto a floured surface and cut into 4.Roll each piece into a 15cm wide log. Cut the log into 2cm pieces using a floured knife. Gently mark each gnocchi with the back of a floured fork to achieve traditional ridges.
Bring a large pan of salted water to the boil. Tip in half the gnocchi and cook for 1-2 mins, until they rise to the surface. Remove with a slotted spoon and cook the remaining gnocchi.
Heat 15g butter and the oil in a large frying pan. Add half the gnocchi and fry for 2 mins or until starting to brown. Chop and add the sage, fry for 1-2 mins, until the gnocchi are golden all over and the sage is crispy. Repeat with the remaining butter, gnocchi and sage leaves.
Serve with black pepper and parmesan.