For the ricotta balls; in a medium bowl, combine the ricotta cheese, cooked spinach, mashed potato, eggs, flour, nutmeg, a ¼ cup grated Parmesan cheese, and season well salt and freshly ground black pepper.
Mix all ingredients with a fork until well combined. Grease a medium baking dish with some olive oil.
Using an ice-cream scoop, scoop balls of ricotta into the baking dish, making sure the balls are packed closely together. Top with Napolitana sauce and place into a preheated 200°C oven. Bake for 40 minutes until bubbling.
Remove from the oven and scatter with grated Parmesan and fresh basil before serving.