Remove stems and roughly chop the spinach. In a pan, sauté the onion and garlic until fragrant, add the chopped, dried spinach and cook until wilted. If you are using frozen spinach be sure to squeeze it to remove al of the moisture from thawing.
Preheat the oven to 375º F.
Coat a small baking dish with cooking spray. If you are using a bread bowl, omit this step
Place the cream cheese, sour cream, mayonnaise, water chestnuts, spinach, salt and pepper, parmesan cheese and 1 cup of the mozzarella cheese and cheddar cheese (if using) in a bowl and stir until well combined. Add the spinach mixture and stir well.
Spread the mixture into the prepared dish (sprayed with non stick spray) and then top with remaining 1/2 cup mozzarella cheese. If using a bread bowl, skip to instructions below.
Bake for 20 minutes or until dip is bubbly and cheese is melted.
Turn the oven to broil and cook for an additional 2-3 minutes or until cheese starts to brown. Remove from oven to cool a bit before serving.
Sprinkle with chopped parsley if using, then serve with bread cubes, crackers and veggie sticks.