A type of gnocchi, gnudi is traditionally made with ricotta cheese which lends a rich and creamy texture to the dish.
Put the spinach with just the water clinging to the leaves after washing into a large pan. Cook over low heat, turning once or twice, for about 3 minutes, until wilted. Drain well, squeezing out as much liquid as possible, and chop very finely. Tip into a bowl and stir in the ricotta, pecorino cheese, eggs, and flour. Add the nutmeg and season with salt and pepper.
Bring a large pan of salted water to a boil. Using a teaspoon, shape small rounded dumplings from the ricotta mixture, dust with flour and add to the pan.
Cook in batches for 2-3 minutes until they float to the surface. Remove with a slotted spoon, drain on a paper towel and transfer to warmed serving dish. Melt the butter with sage in another pan, then pour this over the dumplings and serve.