Wash and dry the spinach.
Place you oil into a large skilling and heat over medium heat, add the garlic and sauté for a minute.
Then pour in the spinach, cover the pan with the lid and let the spinach wilt over medium-low heat for 7-8 minutes.
Once the spinach is cooked transfer to a colander placed on a bowl, to drain the excess liquid, squeezing them with a rubber spatula.
Also place the ricotta on a colander and drain in the same way, as well.
Combine the ricotta and spinach in a large bowl.
Season with pepper and salt and add a generous grating of nutmeg for added flavor.
Then pour in the grated Parmesan, egg, and sift in the flour.
Pinch out a small amount of mixture (about 18-20 g) and shape it into a slightly flattened ball. Pass it in the flour and place it on a tray covered with parchment paper.
Continue with until you have no more mixture left.
Put the gnudi into a pot of boiling salted water.
Meanwhile, in a large skillet, melt the butter over low heat together with the sage.
Boil the gnudi for a few minutes, and as soon as they come to the surface, drain them and transfer them directly to the pan.
Gnudi are pretty delicate, let the gnudi simmer in the butter briefly without turning them, just rotating the pan.
Place on a dish and serve immediatly!