To make this comforting pasta dish, start by preheating the oven to 375 °F. Saute washed spinach in a hot pan with a splash of olive oil. Cook for 4 to 5 minutes, stirring constantly. Season with salt and pepper. Then add ricotta cheese, and stir to get a rich, creamy blend. Stuff each cannelloni with the cheesy spinach preparation. Place them in a baking dish and cover with tomato sauce or béchamel, as you prefer. Bake for 40-45 minutes. Serve immediately with fresh basil leaves to garnish.