Bring a large, wide pot of salted water to a simmer. Put the spinach in a large bowl and separate it with your hands. Add the ricotta, 3/4 cup parmesan, the flour, eggs, 3/4 teaspoon salt, 1/4 teaspoon pepper and the nutmeg. Mix with a fork to form a slightly sticky dough.
Spread some flour on a plate. Scoop out heaping tablespoonfuls of the spinach-ricotta mixture and roll into about 24 loose balls using floured hands. Gently roll the balls in the flour.
Bring the marinara sauce to a simmer in a large skillet over medium heat. Whisk in the butter.
Meanwhile, gently lower the dumplings into the simmering water and cook until they rise to the surface and are firm, about 5 minutes. Remove the dumplings with a slotted spoon, letting the water drain off, and add to the sauce. Gently toss to coat, then transfer to plates and sprinkle with the remaining 1/4 cup parmesan. Serve with bread.
Photograph by Antonis Achilleos
Courtesy of Food Network Magazine