Finely chop the fresh spinach and sauté in a skillet over medium heat for 2-3 minutes until wilted. Remove from heat and let cool.

In a large mixing bowl, combine ground meat, wilted spinach, diced mozzarella, egg, breadcrumbs, salt, and pepper. Mix gently until just combined.

Cover the bowl and refrigerate for 15 minutes to firm the mixture.

Shape the mixture into approximately 12 meatballs.

Cook the meatballs in a skillet over medium-high heat with olive oil, for 8-10 minutes until golden and cooked through, or bake at 200°C (400°F) for 20-25 minutes.

Let the meatballs rest and serve warm with dipping sauce or over pasta.