Cook the pasta in plenty of water until cooked al dente, then drain and set aside.
Meanwhile, add the leek to a food processor, along with the spinach and garlic. Blitz until well chopped. Add the two tins of beans and the fresh parsley, and blitz again thoroughly. Finally add the ricotta and a generous pinch of salt and pepper, and blitz one last time.
Add the sauce to the cooked pasta, and mix to combine. You can add a dash of water or vegetable stock to thin it out a little, if needed.
Add the pasta to a large baking dish, and pour over the passata or tomato sauce. Top with some fresh mozzarella and grated cheddar, and bake at 190°C (Gas Mark 5 / 375°F) for around 30 minutes, or until the cheese has crisped up to your liking.