Wring defrosted spinach dry in a clean kitchen towel.
Place turkey in a bowl and make a well in the middle of it.
Add the spinach, onion, garlic, 1 large egg, about 1/4 cup milk, bread crumbs, grated Parmesan, salt and pepper. Mix well. Form into 12 large balls and drizzle with extra-virgin olive oil. Arrange on a nonstick cookie sheet and roast 20 to 25 minutes (depending on your oven).