Directions
Prep the Oven and Pasta
Preheat your oven to 375°F (190°C). Cook the manicotti shells in a large pot of salted boiling water according to package instructions until al dente (usually about 7–8 minutes). Drain and lay them out on a parchment-lined baking sheet to prevent them from sticking together.
Brown the Beef
In a skillet over medium heat, cook the ground beef and diced onion together until the meat is browned and no longer pink (about 5–7 minutes). Add the minced garlic and cook for another minute until fragrant. Drain any excess grease and allow the mixture to cool slightly.
Mix the Cheese Filling
In a medium bowl, combine the ricotta cheese, 1 cup of mozzarella, Parmesan cheese, beaten egg, chopped parsley, dried oregano, Italian seasoning, salt, and pepper. Stir in the cooked ground beef mixture until fully combined.
Assemble the Dish
Spread 1 cup of marinara sauce across the bottom of an 8x11-inch or 9x13-inch baking dish. Carefully pipe or spoon the beef and cheese filling into each cooked manicotti shell using a spoon or a piping bag/zip-top bag with the corner cut off. Place the filled shells side-by-side in the prepared baking dish.
Sauce and Top
Pour the remaining 1 1/2 cups of marinara sauce evenly over the top of the filled manicotti, ensuring the pasta shells are well covered to keep them moist while baking. Sprinkle the remaining 1/2 cup of mozzarella cheese evenly over the top.
Bake and Serve
Cover the baking dish loosely with aluminum foil and bake for 25 minutes. Remove the foil and bake uncovered for an additional 10 minutes, or until the cheese is melted, bubbly, and lightly golden brown. Allow the manicotti to rest for 5 to 10 minutes to set, then garnish with fresh chopped basil or parsley and serve hot alongside a fresh green salad or garlic bread.