Line a rimmed baking sheet with Gefen Parchment Paper.

In a large bowl, combine spinach with butter, onion, eggs, cheeses, garlic powder, salt, pepper, and panko. Mix well.

Roll mixture into one- an- a- half-inch balls; place onto prepared baking sheet. Refrigerate for 20 minutes, while oven is preheating.

Preheat oven to 350°F. Bake for 25–30 minutes, until golden and piping hot. Serve hot or at room temperature.