Wash, rinse and cook spinach for few minutes in a pan.
Drain them very well and chop roughly.
In a bowl mix ricotta, flour, salt, nutmeg and egg(s), add spinach and mix well.
With slightly wet hands take a small amount of dough, roll it into the shape of a small sausage.
Do it with all the dough then roll the gnudi into the flour.
Bring a big pan of water with salt to the boiling point, put in some gnudi at time, when they float drain them and put into a baking tray.
When you have all your gnudi on the baking tray melt butter with sage and cover gnudi with it and grated parmesan, bake at 360°F for 25-30 minutes or until Parmesan is gold and crispy.
Serve hot.