My mom and I had some palle di spinaci at my friend with a broken foot's the other day. She had made them palle di spinaci herself and explained to me how it was made..
First of all, you cook spinach, drain it and mix it with ricotta cheese. You might also need to add a bit of flour because it would make it stickier and easier to shape the ingredients into balls. If you can't eat it all fresh, you can store them in the freezer.
To serve these balls, you have to first bring the water to a boil before putting these balls in, when them palle float to the surface, they shall be done.
Apparently, if these balls are wrapped inside of pastry, it would turn into Ravioli. (See... we learn something everyday...)
For the sauce, she added some herb into butter or the I can't believe it is not butter.
When serving the dish, you simply pour the sauce on top of palle di spinici and some parmesan cheese as well.
As usual, my mom was very impressed by the Italian immersion experiences!