Start by cooking the jumbo pasta shells according to the instructions on the package. Boil them in a large pot of salted water until they’re al dente. Drain and rinse gently under cold water to stop the cooking process.

In a skillet over medium heat, add the ground beef and brown evenly. Break it apart with a spatula while cooking. When no longer pink, add the finely diced onion and minced garlic, cooking until onions are softened and translucent, about 5 minutes.

Sprinkle in the Italian seasoning, salt, and pepper, stirring everything together to bloom the spices for another minute. Taste and adjust seasoning as needed.

In a mixing bowl, combine the beef mixture with ricotta cheese, half of the shredded mozzarella, grated Parmesan, beaten egg, and chopped parsley. Blend until well mixed.

Preheat your oven to 350 degrees Fahrenheit. Pour 1 cup of marinara sauce into the bottom of a baking or casserole dish.

Gently fill each cooked shell with the beef and cheese mixture, placing them seam side up in the dish.

Pour the remaining marinara sauce over the stuffed shells and sprinkle the remaining mozzarella and extra Parmesan on top.

Cover with aluminum foil and bake for about 30 minutes. Uncover to ensure the cheese is melted beautifully.