Place the spinach and water in a large microwave-save bowl. Cover the bowl with a large dinner plate. Microwave on high until the spinach is wilted and decreased in volume by half (about 5 minutes). Carefully remove the bowl from the microwave and keep covered for 1 minute.
Remove the plate and transfer the spinach to a colander in the sink. Using the back of a rubber spatula, press the spinach against the colander to release the excess liquid. Transfer the spinach to a cutting board and roughly chop. Wrap the spinach in paper towels and squeeze to remove excess water. Transfer the spinach to a large bowl. Add the remaining ingredients (except the butter, pecorino cheese, and phyllo pastry) to the bowl and mix until thoroughly combined.