Preheat oven to 350 degrees F.

Cook pasta shells according to package directions.

Prepare a 9 X 13-inch baking dish by spraying it with cooking spray.

Pour the olive oil into a skillet and warm over medium heat.

Sautée the garlic and onion until fragrant, about 3 minutes.

Add the ground beef to the skillet and cook until brown.

Pour in the pasta sauce and simmer on low until ready to use.

In a large mixing bowl, beat the egg. Add the ricotta cheese, 1 cup of the mozzarella, Parmesan cheese and parsley. Mix well.

Place 1/3 of the meat sauce into the bottom of the prepared baking dish.

Fill each shell with the filling and place into the baking dish.

Pour remaining meat sauce over the shells and cover the pan with tin foil.

Bake for 30 minutes.

Remove tin foil and sprinkle the remaining 1 cup of mozzarella over the shells. Return to oven to bake for another 5 - 10 minutes or until cheese is melted.