How to Make It
Heat a skillet. Add the spinach by handfuls and cook over high heat, stirring, until just wilted. Transfer the spinach to a colander and press out the excess water. Finely chop the spinach.
In a large bowl, combine the spinach with the eggs, egg yolks, ricotta, grated Parmesan, 2 teaspoons kosher salt, 1/4 teaspoon pepper and the nutmeg; stir well. Add the flour and stir just until combined; the dough will be soft and sticky.
Scoop out rounded teaspoons of the dough onto a well-floured work surface, and roll each piece into a ball. On lightly floured baking sheets, arrange the balls so they aren't touching.
Bring a large saucepan of salted water to a boil. In a medium saucepan, simmer the cream and minced sage over low heat, stirring, until slightly thickened, about 12 minutes. Season with salt and pepper; keep warm.
Cook the gnocchi in the boiling water until they rise to the surface, about 5 minutes. Transfer the gnocchi to a shallow bowl. Pour the sage sauce over the gnocchi. Garnish with the sage leaves and Parmesan shavings and serve.