2) Brush one teaspoon of oil over a large baking sheet. Cook the manicotti in a large pot of boiling salted water until slightly softened, but still very firm to the bite, about 4-6 minutes. Using a slotted spoon, transfer the manicotti from the pot to the oiled baking sheet and cool.
3) Meanwhile, combine the ricotta, 150 to 200g mozzarella cheese, 50g Parmesan, and parsley. Add the garlic, salt, and pepper to taste, and mix. Stir the cooled meat mixture into the cheese mixture.
4) Preheat the oven to 180°C/gas mark 4.
5) Brush the remaining 2 teaspoons of oil over a 28cm x 23cm c 5cm glass baking dish. Spoon 375ml of the marinara sauce over the bottom of the prepared dish. Fill the canneloni with the cheese-meat mixture. Arrange the stuffed pasta in a single layer in the prepared dish and spoon the remaining sauce over.
6) Sprinkle the remaining mozzarella cheese, then the remaining 50g of Parmesan over the stuffed pasta. Dot entire dish with the butter pieces. Bake the manicotti uncovered until heated through and the sauce bubbles on the sides of the dish, about 30 to 35 minutes. Let the canneloni stand 5 minutes and serve.