Clean, wash and cook the spinach (using just the water left over on the leaves after washing). Drain, squeeze well and chop finely. Wilt the minced onion in 2 oz. of butter, then drain the onion and add it to the spinach. Cook on a very low heat, stirring frequently to allow the spinach to exude more water, then let cool.
Sieve the ricotta into a bowl. Add the spinach, about 2 oz. of Parmigiano, 2 whole eggs and 1 yolk, a pinch of nutmeg, and pepper and salt to taste. Mix, adding in the flour little by little, as much as necessary to obtain a firm but soft mix. Use a spoon to make dumplings the size of a walnut. Lightly sprinkle gnocchi with flour (the amount of flour used to dust them will vary according to how well the spinach is dried), and set aside on a sheet pan.
Bring a generous amount of salted water to a boil in a large pot. Meanwhile, brown the rest of the butter in a saucepan, adding whole sage leaves to taste. Add gnocchi to the boiling water, stirring gently. As they float to the top drain with a skimmer and arrange in a serving platter. Season with the sage flavored melted butter and Parmigiano. Serve very hot. Instead of sage-flavored butter, you may use a light tomato sauce.
Note:
In order to allow the condiment to develop its full favor, keep care to warm the platter with gnocchi in a bain-marie for 5 mins. before serving.
