• Preheat the oven to 350 degrees F. Coat a 9"x13" baking dish with cooking spray.

For the filling

• Heat the olive oil in a large pan over medium heat. Place the sausage in the pan. Cook for 3-4 minutes, breaking up the meat into small pieces.
• Add the onions to the pan. Cook for an additional 4-5 minutes or until onions are softened and sausage is browned and cooked through.
• Add the garlic and cook for an additional 30 seconds. Remove the pan from the heat.
• Place the ricotta cheese, egg, mozzarella, parmesan, Italian seasoning and salt and pepper in a large bowl. Stir to combine.
• Add the meat mixture to the ricotta mixture. Stir until well mixed.

For assembly

• Cook the manicotti in salted boiling water for 1-2 minutes less than the package directions state. Drain and cool slightly.
• Spread 1 cup of the marinara sauce over the bottom of the pan.
• Use a spoon or piping bag to fill each manicotti with the meat and cheese mixture.
• Arrange the manicotti in a single layer in the pan. Pour the rest of the sauce over the top.
• Cover and bake for 20 minutes. Uncover, sprinkle the mozzarella cheese over the top, then bake for an additional 10-15 minutes or until cheese is melted and browned.
• Sprinkle with parsley, then serve.