Prepare the Spinach

1. Thaw the Spinach: Start by thawing the frozen spinach in the microwave or by letting it sit at room temperature. Once thawed, place the spinach in a fine mesh strainer or cheesecloth and press out as much water as possible.
2. Chop the Spinach: After removing the water, chop the spinach into small pieces to help distribute the flavor evenly throughout the balls.

Mix the Ingredients

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or lightly grease it.
2. Combine Ingredients: In a large bowl, mix the spinach, breadcrumbs, Parmesan, mozzarella, beaten eggs, chopped onion, garlic, olive oil, and herbs. Season with salt and pepper.
3. Mix Until Well Combined: Stir everything together until fully combined. You should have a thick, sticky mixture.

Form the Spinach Balls

1. Shape the Balls: Scoop about a tablespoon of the spinach mixture and roll it into a ball. Continue until all the mixture is used up.
2. Roll in Parmesan (Optional): For an extra cheesy finish, roll each spinach ball in the remaining grated Parmesan before placing it on the baking sheet.

Bake the Spinach Balls

1. Bake: Place the spinach balls on the prepared baking sheet, spacing them about an inch apart. Bake for 20-25 minutes, or until the balls are golden brown and crispy on the outside.
2. Cool Slightly: Let the spinach balls cool for a few minutes before serving.