01 - Preheat oven to 350°F (180°C) and line a baking sheet with parchment paper.
02 - Wilt fresh spinach in a large pan over medium heat for 2 to 3 minutes until just softened. Transfer to a colander, cool, and squeeze out excess moisture.
03 - In a large mixing bowl, combine spinach, onion, garlic, mozzarella, Parmesan, eggs, breadcrumbs, baking powder, nutmeg, salt, pepper, parsley, and chili flakes if using.
04 - Mix until well combined and the mixture holds together when pressed.
05 - Using hands or a small scoop, shape mixture into bite-sized balls (approximately 1 tablespoon each) and place them on the prepared baking sheet.
06 - Bake for 18 to 20 minutes, or until golden brown and set.
07 - Let cool slightly before serving warm, optionally with preferred dips.