Preheat oven to 375 F.

Bring a large pot of water to a boil. Once water is boiling, add the shells. Cook for about 15 minutes, until soft. Drain and set aside.

In a large bowl, add ricotta, 1 cup of mozzarella, ⅓ cup of parmesan, egg, oregano, salt and pepper. Mix well to combine.

Roughly chop baby spinach and mix into the cheese mixture.

Spread 1 cup of tomato sauce in an even layer on top of a 9x13 baking sheet.

Stuff each shell with 1 large spoonful of cheese mixture and place on top of the tomato sauce on the baking sheet.

Spoon the additional ½ cup tomato sauce over the shells and top with the ¼ cup mozzarella and remaining ⅓ cup of parmesan cheese.

Place in the oven and bake for 20 minutes. Turn the oven to broil and broil for another 3-5 minutes, until the cheese on top is golden but not burned.

Optional: garnish with fresh chopped parsley and serve.