1) Preheat the oven to 190C/Gas Mark 5. Blanch the spinach in water. Drain and chop. Mix the ricotta cheese with the spinach. Add the Parmesan and the flour. Mix well. Add a pinch of salt and pepper. Take 1 tbsp full of the ricotta mixture and form small balls with your hand (about 1cm). Place in a casserole dish.
2) Add some tomato sauce over the ricotta-spinach balls. Sprinkle some Parmesan over and cook for 10 mins.