Microwave the frozen spinach to defrost if you haven’t done so already. Drain off excess moisture if it’s too watery.
In a large bowl, combine the ricotta cheese, eggs, grated parmesan, breadcrumbs, spinach, salt, and pepper. Mix until just combined.
Shape the mixture into small meatballs, about 3–4 cm in diameter. You should get around 25 meatballs.
Pour the jar of basil pasta sauce or passata into a baking dish, spreading it evenly across the bottom.
Place the meatballs on top of the passata in the baking dish, arranging them in a single layer.
Bake in the preheated oven for 40–50 minutes, or until the meatballs are golden and cooked through. The sauce should be bubbly and slightly thickened.
Once baked, serve the meatballs directly from the dish, spooning some of the sauce over the top. Serve with crusty bread, pasta, rice, or any preferred sides.