To prepare a zavioli with spinach and ricotta recipe, you'll first need to prepare the spinach. You can buy frozen spinach at your local grocery store, or you can use fresh spinach that has been thawed in the refrigerator. If you want to make your own spinach, cut the stems off of the stalks and chop them into small cubes. Add the cubed spinach to the boiling water and cook until it's just wilted, about 5 minutes. Drain the water, and then add the drained spinach into the hot water. Cover the pot and let it boil for 5 to 10 minutes, until all the liquid has evaporated. Remove the pan from the heat and allow it to cool for 10 to 15 minutes before serving.