Preheat the oven to 425°F (220°C) and line a baking sheet with parchment paper.
In a medium saucepan, bring the water, butter, salt, and ground black pepper to a boil. Add the flour and stir until it forms a dough. Cook for an additional 2 minutes to dry out the dough.
Transfer the dough to a bowl and let it cool slightly. Slowly add the eggs, one at a time, stirring until well combined.
Add the mozzarella cheese and parsley, and mix well. Using 2 tablespoons, shape each ball of dough and drop it onto the prepared parchment paper, spacing them 1.5 to 2 inches (4 to 5 cm) apart. Sprinkle some grated Parmesan cheese on top.
Bake for 10 minutes at 425°F (220°C), then reduce the temperature to 380°F (190°C) and continue baking for another 20–25 minutes, or until golden brown. Serve warm.
Notes
You can use any type of grated cheese or herb for this recipe.