Traditional Italian gnocchi are made with potatoes and are often heavy going. This version substitutes ricotta cheese and a small amount of flour for the starch. Spinach and herbs contribute flavor, color, and texture; the result is a light, melt-in-your mouth sensation.These gnocchi are very fragile, so take care in the cooking. The dough, minus the flour, also makes an excellent stuffing for pasta shells or ravioli. Serve with your favorite marinara or Alfredo sauce.
Place a steamer basket or insert into a large pot. Add an inch of water and place the spinach and arugula leaves in the steamer. Bring to a boil over high heat and cook until the greens are wilted, about 2 minutes. Transfer the greens to a sieve and let cool.
Purée the basil, parsley, and scallions in a food processor until smooth. Transfer the purée to a large bowl.
When the wilted greens are cool enough to handle, squeeze out all the moisture. A linen or cotton kitchen towel is helpful. All the water must be removed or the gnocchis will be too soft. Transfer the greens to the food processor and purée. Add the egg, ricotta, parmesan, salt, pepper, nutmeg, and herb purée, and pulse to blend the mixture.
Transfer the gnocchi mixture to a bowl and stir in the flour, blending just to combine. Refrigerate the dough for at least 2 hours to allow it to firm.
The easiest way to form gnocchis is with a large pastry bag and a #16 round tip. Place a lightly floured sheet of wax or parchment paper on the counter. Pipe out a ribbon of dough, cutting it with scissors at 3/4-inch intervals. Let the gnocchis fall gently onto the paper, separating them so they do not touch one another. You also can form them by hand if you don't have a pastry bag. Roll one-fourth of the dough into a long 1/2-inch-thick rope, and cut at 3/4-inch intervals with a sharp knife. Try to attain a uniform size and shape so the gnocchi will cook evenly.
To cook, bring a large pot of lightly salted water to a simmer over medium heat. Add a third of the gnocchis and poach in the gently simmering water (adjust burner as needed) until the gnocchis float to the surface, 2 to 3 minutes. Do not allow the water to boil or the gnocchis will disintegrate. Remove from the water with a slotted spoon and cool on a lightly buttered platter; do not stack or allow gnocchis to touch one another. Repeat with the remaining dough.
Add cooked gnocchis to a warm sauce; or cool them and refrigerate for up to 2 days; or freeze them for 1 month in a tightly sealed plastic bag. Gnocchis can be reheated easily in the microwave.