Saute spinach until soft. Let cool.
In a bowl mix Ricotta, egg yolk, Parmigiano-Reggiano, nutmeg, salt and 2 Tbsp fresh basil.
Fill a small bowl with water. Lay several won ton wrappers in front of you. Put 1 tsp of filling in the middle of each wrapper. Wet your fingers in the water and lightly rub water around the edges of the wrapper (this will help the edges stick together and seal). Fold the wrapper into the shape of a triangle. Pinch the edges of the wrapper so they seal and create a dumpling. Continue this process until all the filling is used.
Put a pot of water on to boil. Cook the dumplings in the boiling water in batches of 8-10 until they rise to the top of the pot, about 3 minutes. Set the cooked dumplings on a plate or cookie sheet.
When all the dumplings have been boiled, warm 1 Tbsp of butter or olive oil in a pan. Saute the dumplings in batches, adding more butter or oil as needed, so that the edges of the dumplings become slightly crispy.
Before serving, garnish dumplings with more grated Parmigiano-Reggiano cheese and the remaining fresh basil.