1. Saute 1 tsp olive oil, onion, and ground beef seasoned with salt and pepper. Saute until meat browns and the onion is translucent, about 5 min. Remove from heat.
2. Cook manicotti until slightly softened, but still firm to the bite, about 4-6 min. Transfer from water to lightly greased baking sheet.
3. Combine ricotta, 1.5-2 cups mozzarella cheese, 1/2 cup parmesan, and parsley. Add garlic, salt, and pepper to taste and mix. Stir together the meat mixture and the cheese mixture.
4. Preheat oven to 350.
5. Brush remaining olive oil in 9x13 baking dish. Spoon 1 1/2 cups marinara over the bottom of the dish. Fill the manicotti with the meat and cheese mixture. Arrange in a single layer in the dish and spoon over remaining sauce.
6. Sprinkle 1.5 cups of cheese and the remaining 1/2 cup of parmesan over the stuffed pasta. Dot entire dish with butter pieces (optional). Bake uncovered until heated through and the sauce bubbles on the sides of the dish, about 30-35 min.
